Get rid of internal tests

Move all tests to e2e+ level

CliFx.Benchmarks/Benchmarks.cs

@@ -18,7 +18,7 @@ namespace CliFx.Benchmarks
 
         [Benchmark(Description = "CliFx", Baseline = true)]
         public async ValueTask<int> ExecuteWithCliFx() =>
-            await new CliApplicationBuilder().AddCommand(typeof(CliFxCommand)).Build().RunAsync(Arguments, new Dictionary<string, string>());
+            await new CliApplicationBuilder().AddCommand<CliFxCommand>().Build().RunAsync(Arguments, new Dictionary<string, string>());
 
         [Benchmark(Description = "System.CommandLine")]
         public async Task<int> ExecuteWithSystemCommandLine() =>

CliFx.Tests/ApplicationSpecs.Commands.cs

@@ -1,179 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class ApplicationSpecs
-    {
-        [Command]
-        private class DefaultCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class AnotherDefaultCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class NonImplementedCommand
-        {
-        }
-
-        private class NonAnnotatedCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("dup")]
-        private class DuplicateNameCommandA : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("dup")]
-        private class DuplicateNameCommandB : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateParameterOrderCommand : ICommand
-        {
-            [CommandParameter(13)]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(13)]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateParameterNameCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param")]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(1, Name = "param")]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class MultipleNonScalarParametersCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public IReadOnlyList<string>? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public IReadOnlyList<string>? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class NonLastNonScalarParameterCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public IReadOnlyList<string>? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class EmptyOptionNameCommand : ICommand
-        {
-            [CommandOption("")]
-            public string? Apples { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class SingleCharacterOptionNameCommand : ICommand
-        {
-            [CommandOption("a")]
-            public string? Apples { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionNamesCommand : ICommand
-        {
-            [CommandOption("fruits")]
-            public string? Apples { get; set; }
-
-            [CommandOption("fruits")]
-            public string? Oranges { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionShortNamesCommand : ICommand
-        {
-            [CommandOption('x')]
-            public string? OptionA { get; set; }
-
-            [CommandOption('x')]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ConflictWithHelpOptionCommand : ICommand
-        {
-            [CommandOption("option-h", 'h')]
-            public string? OptionH { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ConflictWithVersionOptionCommand : ICommand
-        {
-            [CommandOption("version")]
-            public string? Version { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionEnvironmentVariableNamesCommand : ICommand
-        {
-            [CommandOption("option-a", EnvironmentVariableName = "ENV_VAR")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", EnvironmentVariableName = "ENV_VAR")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("hidden", Description = "Description")]
-        private class HiddenPropertiesCommand : ICommand
-        {
-            [CommandParameter(13, Name = "param", Description = "Param description")]
-            public string? Parameter { get; set; }
-
-            [CommandOption("option", 'o', Description = "Option description", EnvironmentVariableName = "ENV")]
-            public string? Option { get; set; }
-
-            public string? HiddenA { get; set; }
-
-            public bool? HiddenB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/ApplicationSpecs.cs

@@ -1,14 +1,15 @@
 using System;
 using System.IO;
-using CliFx.Domain;
+using System.Threading.Tasks;
-using CliFx.Exceptions;
+using CliFx.Tests.Commands;
+using CliFx.Tests.Commands.Invalid;
 using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class ApplicationSpecs
+    public class ApplicationSpecs
     {
         private readonly ITestOutputHelper _output;
 
@@ -31,7 +32,7 @@ namespace CliFx.Tests
         {
             // Act
             var app = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
+                .AddCommand<DefaultCommand>()
                 .AddCommandsFrom(typeof(DefaultCommand).Assembly)
                 .AddCommands(new[] {typeof(DefaultCommand)})
                 .AddCommandsFrom(new[] {typeof(DefaultCommand).Assembly})
@@ -51,219 +52,356 @@ namespace CliFx.Tests
         }
 
         [Fact]
-        public void At_least_one_command_must_be_defined_in_an_application()
+        public async Task At_least_one_command_must_be_defined_in_an_application()
         {
-            // Arrange
+            await using var stdErr = new MemoryStream();
-            var commandTypes = Array.Empty<Type>();
+            var console = new VirtualConsole(error: stdErr);
 
-            // Act & assert
+            var application = new CliApplicationBuilder()
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
+                .UseConsole(console)
-            _output.WriteLine(ex.Message);
+                .Build();
-        }
-
-        [Fact]
-        public void Commands_must_implement_the_corresponding_interface()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonImplementedCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Commands_must_be_annotated_by_an_attribute()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonAnnotatedCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Commands_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateNameCommandA), typeof(DuplicateNameCommandB)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_can_be_default_but_only_if_it_is_the_only_such_command()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DefaultCommand), typeof(AnotherDefaultCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_parameters_must_have_unique_order()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateParameterOrderCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_parameters_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateParameterNameCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_parameter_can_be_non_scalar_only_if_no_other_such_parameter_is_present()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(MultipleNonScalarParametersCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_parameter_can_be_non_scalar_only_if_it_is_the_last_in_order()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonLastNonScalarParameterCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_have_names_that_are_not_empty()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(EmptyOptionNameCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_have_names_that_are_longer_than_one_character()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(SingleCharacterOptionNameCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionNamesCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_short_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionShortNamesCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_not_have_conflicts_with_the_implicit_help_option()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(ConflictWithHelpOptionCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_not_have_conflicts_with_the_implicit_version_option()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(ConflictWithVersionOptionCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_environment_variable_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionEnvironmentVariableNamesCommand)};
-
-            // Act & assert
-            var ex = Assert.Throws<CliFxException>(() => RootSchema.Resolve(commandTypes));
-            _output.WriteLine(ex.Message);
-        }
-
-        [Fact]
-        public void Command_options_and_parameters_must_be_annotated_by_corresponding_attributes()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(HiddenPropertiesCommand)};
 
             // Act
-            var schema = RootSchema.Resolve(commandTypes);
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
-            schema.Should().BeEquivalentTo(new RootSchema(new[]
+            exitCode.Should().NotBe(0);
-            {
+            stdErrData.Should().NotBeEmpty();
-                new CommandSchema(
-                    typeof(HiddenPropertiesCommand),
-                    "hidden",
-                    "Description",
-                    new[]
-                    {
-                        new CommandParameterSchema(
-                            typeof(HiddenPropertiesCommand).GetProperty(nameof(HiddenPropertiesCommand.Parameter))!,
-                            13,
-                            "param",
-                            "Param description")
-                    },
-                    new[]
-                    {
-                        new CommandOptionSchema(
-                            typeof(HiddenPropertiesCommand).GetProperty(nameof(HiddenPropertiesCommand.Option))!,
-                            "option",
-                            'o',
-                            "ENV",
-                            false,
-                            "Option description"),
-                        CommandOptionSchema.HelpOption
-                    })
-            }));
 
-            schema.ToString().Should().NotBeNullOrWhiteSpace(); // this is only for coverage, I'm sorry
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Commands_must_implement_the_corresponding_interface()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand(typeof(NonImplementedCommand))
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Commands_must_be_annotated_by_an_attribute()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<NonAnnotatedCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Commands_must_have_unique_names()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<GenericExceptionCommand>()
+                .AddCommand<CommandExceptionCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_can_be_default_but_only_if_it_is_the_only_such_command()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<OtherDefaultCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_parameters_must_have_unique_order()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DuplicateParameterOrderCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_parameters_must_have_unique_names()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DuplicateParameterNameCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_parameter_can_be_non_scalar_only_if_no_other_such_parameter_is_present()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<MultipleNonScalarParametersCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_parameter_can_be_non_scalar_only_if_it_is_the_last_in_order()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<NonLastNonScalarParameterCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_have_names_that_are_not_empty()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<EmptyOptionNameCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_have_names_that_are_longer_than_one_character()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<SingleCharacterOptionNameCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_have_unique_names()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DuplicateOptionNamesCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_have_unique_short_names()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DuplicateOptionShortNamesCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_have_unique_environment_variable_names()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DuplicateOptionEnvironmentVariableNamesCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_not_have_conflicts_with_the_implicit_help_option()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<ConflictWithHelpOptionCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
+        }
+
+        [Fact]
+        public async Task Command_options_must_not_have_conflicts_with_the_implicit_version_option()
+        {
+            await using var stdErr = new MemoryStream();
+            var console = new VirtualConsole(error: stdErr);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<ConflictWithVersionOptionCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().NotBe(0);
+            stdErrData.Should().NotBeEmpty();
+
+            _output.WriteLine(stdErrData);
         }
     }
 }

CliFx.Tests/ArgumentBindingSpecs.Commands.cs

@@ -1,197 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class ArgumentBindingSpecs
-    {
-        [Command]
-        private class AllSupportedTypesCommand : ICommand
-        {
-            [CommandOption(nameof(Object))]
-            public object? Object { get; set; } = 42;
-
-            [CommandOption(nameof(String))]
-            public string? String { get; set; } = "foo bar";
-
-            [CommandOption(nameof(Bool))]
-            public bool Bool { get; set; }
-
-            [CommandOption(nameof(Char))]
-            public char Char { get; set; }
-
-            [CommandOption(nameof(Sbyte))]
-            public sbyte Sbyte { get; set; }
-
-            [CommandOption(nameof(Byte))]
-            public byte Byte { get; set; }
-
-            [CommandOption(nameof(Short))]
-            public short Short { get; set; }
-
-            [CommandOption(nameof(Ushort))]
-            public ushort Ushort { get; set; }
-
-            [CommandOption(nameof(Int))]
-            public int Int { get; set; }
-
-            [CommandOption(nameof(Uint))]
-            public uint Uint { get; set; }
-
-            [CommandOption(nameof(Long))]
-            public long Long { get; set; }
-
-            [CommandOption(nameof(Ulong))]
-            public ulong Ulong { get; set; }
-
-            [CommandOption(nameof(Float))]
-            public float Float { get; set; }
-
-            [CommandOption(nameof(Double))]
-            public double Double { get; set; }
-
-            [CommandOption(nameof(Decimal))]
-            public decimal Decimal { get; set; }
-
-            [CommandOption(nameof(DateTime))]
-            public DateTime DateTime { get; set; }
-
-            [CommandOption(nameof(DateTimeOffset))]
-            public DateTimeOffset DateTimeOffset { get; set; }
-
-            [CommandOption(nameof(TimeSpan))]
-            public TimeSpan TimeSpan { get; set; }
-
-            [CommandOption(nameof(CustomEnum))]
-            public CustomEnum CustomEnum { get; set; }
-
-            [CommandOption(nameof(IntNullable))]
-            public int? IntNullable { get; set; }
-
-            [CommandOption(nameof(CustomEnumNullable))]
-            public CustomEnum? CustomEnumNullable { get; set; }
-
-            [CommandOption(nameof(TimeSpanNullable))]
-            public TimeSpan? TimeSpanNullable { get; set; }
-
-            [CommandOption(nameof(TestStringConstructable))]
-            public StringConstructable? TestStringConstructable { get; set; }
-
-            [CommandOption(nameof(TestStringParseable))]
-            public StringParseable? TestStringParseable { get; set; }
-
-            [CommandOption(nameof(TestStringParseableWithFormatProvider))]
-            public StringParseableWithFormatProvider? TestStringParseableWithFormatProvider { get; set; }
-
-            [CommandOption(nameof(ObjectArray))]
-            public object[]? ObjectArray { get; set; }
-
-            [CommandOption(nameof(StringArray))]
-            public string[]? StringArray { get; set; }
-
-            [CommandOption(nameof(IntArray))]
-            public int[]? IntArray { get; set; }
-
-            [CommandOption(nameof(CustomEnumArray))]
-            public CustomEnum[]? CustomEnumArray { get; set; }
-
-            [CommandOption(nameof(IntNullableArray))]
-            public int?[]? IntNullableArray { get; set; }
-
-            [CommandOption(nameof(TestStringConstructableArray))]
-            public StringConstructable[]? TestStringConstructableArray { get; set; }
-
-            [CommandOption(nameof(Enumerable))]
-            public IEnumerable? Enumerable { get; set; }
-
-            [CommandOption(nameof(StringEnumerable))]
-            public IEnumerable<string>? StringEnumerable { get; set; }
-
-            [CommandOption(nameof(StringReadOnlyList))]
-            public IReadOnlyList<string>? StringReadOnlyList { get; set; }
-
-            [CommandOption(nameof(StringList))]
-            public List<string>? StringList { get; set; }
-
-            [CommandOption(nameof(StringHashSet))]
-            public HashSet<string>? StringHashSet { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ArrayOptionCommand : ICommand
-        {
-            [CommandOption("option", 'o')]
-            public IReadOnlyList<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class RequiredOptionCommand : ICommand
-        {
-            [CommandOption(nameof(Option), IsRequired = true)]
-            public string? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class RequiredArrayOptionCommand : ICommand
-        {
-            [CommandOption(nameof(Option), IsRequired = true)]
-            public IReadOnlyList<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ParametersCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public string? ParameterB { get; set; }
-
-            [CommandParameter(2)]
-            public IReadOnlyList<string>? ParameterC { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class UnsupportedPropertyTypeCommand : ICommand
-        {
-            [CommandOption(nameof(Option))]
-            public DummyType? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class UnsupportedEnumerablePropertyTypeCommand : ICommand
-        {
-            [CommandOption(nameof(Option))]
-            public CustomEnumerable<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class NoParameterCommand : ICommand
-        {
-            [CommandOption(nameof(OptionA))]
-            public string? OptionA { get; set; }
-
-            [CommandOption(nameof(OptionB))]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/ArgumentBindingSpecs.Types.cs

@@ -1,53 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-namespace CliFx.Tests
-{
-    public partial class ArgumentBindingSpecs
-    {
-        private enum CustomEnum
-        {
-            Value1 = 1,
-            Value2 = 2,
-            Value3 = 3
-        }
-
-        private class StringConstructable
-        {
-            public string Value { get; }
-
-            public StringConstructable(string value) => Value = value;
-        }
-
-        private class StringParseable
-        {
-            public string Value { get; }
-
-            private StringParseable(string value) => Value = value;
-
-            public static StringParseable Parse(string value) => new StringParseable(value);
-        }
-
-        private class StringParseableWithFormatProvider
-        {
-            public string Value { get; }
-
-            private StringParseableWithFormatProvider(string value) => Value = value;
-
-            public static StringParseableWithFormatProvider Parse(string value, IFormatProvider formatProvider) =>
-                new StringParseableWithFormatProvider(value + " " + formatProvider);
-        }
-
-        private class DummyType
-        {
-        }
-
-        public class CustomEnumerable<T> : IEnumerable<T>
-        {
-            public IEnumerator<T> GetEnumerator() => ((IEnumerable<T>) Array.Empty<T>()).GetEnumerator();
-
-            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
-        }
-    }
-}

CliFx.Tests/ArgumentSyntaxSpecs.cs

@@ -1,378 +0,0 @@
-using System;
-using System.Collections.Generic;
-using CliFx.Domain;
-using CliFx.Tests.Internal;
-using FluentAssertions;
-using Xunit;
-
-namespace CliFx.Tests
-{
-    public class ArgumentSyntaxSpecs
-    {
-        [Fact]
-        public void Input_is_empty_if_no_arguments_are_provided()
-        {
-            // Arrange
-            var arguments = Array.Empty<string>();
-            var commandNames = Array.Empty<string>();
-
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(CommandInput.Empty);
-        }
-
-        public static object[][] DirectivesTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"[preview]"},
-                new CommandInputBuilder()
-                    .AddDirective("preview")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "[debug]"},
-                new CommandInputBuilder()
-                    .AddDirective("preview")
-                    .AddDirective("debug")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(DirectivesTestData))]
-        internal void Directive_can_be_enabled_by_specifying_its_name_in_square_brackets(IReadOnlyList<string> arguments, CommandInput expectedInput)
-        {
-            // Arrange
-            var commandNames = Array.Empty<string>();
-
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] OptionsTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"--option"},
-                new CommandInputBuilder()
-                    .AddOption("option")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "value"},
-                new CommandInputBuilder()
-                    .AddOption("option", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "value1", "value2"},
-                new CommandInputBuilder()
-                    .AddOption("option", "value1", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "same value"},
-                new CommandInputBuilder()
-                    .AddOption("option", "same value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "--option2"},
-                new CommandInputBuilder()
-                    .AddOption("option1")
-                    .AddOption("option2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "--option2", "value2"},
-                new CommandInputBuilder()
-                    .AddOption("option1", "value1")
-                    .AddOption("option2", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "value2", "--option2", "value3", "value4"},
-                new CommandInputBuilder()
-                    .AddOption("option1", "value1", "value2")
-                    .AddOption("option2", "value3", "value4")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "value2", "--option2"},
-                new CommandInputBuilder()
-                    .AddOption("option1", "value1", "value2")
-                    .AddOption("option2")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(OptionsTestData))]
-        internal void Option_can_be_set_by_specifying_its_name_after_two_dashes(IReadOnlyList<string> arguments, CommandInput expectedInput)
-        {
-            // Arrange
-            var commandNames = Array.Empty<string>();
-
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] ShortOptionsTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"-o"},
-                new CommandInputBuilder()
-                    .AddOption("o")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "value"},
-                new CommandInputBuilder()
-                    .AddOption("o", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "value1", "value2"},
-                new CommandInputBuilder()
-                    .AddOption("o", "value1", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "same value"},
-                new CommandInputBuilder()
-                    .AddOption("o", "same value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "-b"},
-                new CommandInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "-b", "value2"},
-                new CommandInputBuilder()
-                    .AddOption("a", "value1")
-                    .AddOption("b", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "value2", "-b", "value3", "value4"},
-                new CommandInputBuilder()
-                    .AddOption("a", "value1", "value2")
-                    .AddOption("b", "value3", "value4")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "value2", "-b"},
-                new CommandInputBuilder()
-                    .AddOption("a", "value1", "value2")
-                    .AddOption("b")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc"},
-                new CommandInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc", "value"},
-                new CommandInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc", "value1", "value2"},
-                new CommandInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c", "value1", "value2")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(ShortOptionsTestData))]
-        internal void Option_can_be_set_by_specifying_its_short_name_after_a_single_dash(IReadOnlyList<string> arguments, CommandInput expectedInput)
-        {
-            // Arrange
-            var commandNames = Array.Empty<string>();
-
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] ParametersTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"foo"},
-                new CommandInputBuilder()
-                    .AddParameter("foo")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"foo", "bar"},
-                new CommandInputBuilder()
-                    .AddParameter("foo")
-                    .AddParameter("bar")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "foo"},
-                new CommandInputBuilder()
-                    .AddDirective("preview")
-                    .AddParameter("foo")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"foo", "--option", "value", "-abc"},
-                new CommandInputBuilder()
-                    .AddParameter("foo")
-                    .AddOption("option", "value")
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "[debug]", "foo", "bar", "--option", "value", "-abc"},
-                new CommandInputBuilder()
-                    .AddDirective("preview")
-                    .AddDirective("debug")
-                    .AddParameter("foo")
-                    .AddParameter("bar")
-                    .AddOption("option", "value")
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(ParametersTestData))]
-        internal void Parameter_can_be_set_by_specifying_the_value_directly(IReadOnlyList<string> arguments, CommandInput expectedInput)
-        {
-            // Arrange
-            var commandNames = Array.Empty<string>();
-
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] CommandNameTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"cmd"},
-                new[] {"cmd"},
-                new CommandInputBuilder()
-                    .SetCommandName("cmd")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"cmd"},
-                new[] {"cmd", "foo", "bar", "-o", "value"},
-                new CommandInputBuilder()
-                    .SetCommandName("cmd")
-                    .AddParameter("foo")
-                    .AddParameter("bar")
-                    .AddOption("o", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"cmd", "cmd sub"},
-                new[] {"cmd", "sub", "foo"},
-                new CommandInputBuilder()
-                    .SetCommandName("cmd sub")
-                    .AddParameter("foo")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(CommandNameTestData))]
-        internal void Command_name_is_matched_from_arguments_that_come_before_parameters(
-            IReadOnlyList<string> commandNames,
-            IReadOnlyList<string> arguments,
-            CommandInput expectedInput)
-        {
-            // Act
-            var input = CommandInput.Parse(arguments, commandNames);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-    }
-}

CliFx.Tests/CancellationSpecs.Commands.cs

@@ -1,27 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class CancellationSpecs
-    {
-        [Command("cancel")]
-        private class CancellableCommand : ICommand
-        {
-            public async ValueTask ExecuteAsync(IConsole console)
-            {
-                try
-                {
-                    await Task.Delay(TimeSpan.FromSeconds(3), console.GetCancellationToken());
-                    console.Output.WriteLine("Never printed");
-                }
-                catch (OperationCanceledException)
-                {
-                    console.Output.WriteLine("Cancellation requested");
-                    throw;
-                }
-            }
-        }
-    }
-}

CliFx.Tests/CancellationSpecs.cs

@@ -1,14 +1,14 @@
 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
 
 namespace CliFx.Tests
 {
-    public partial class CancellationSpecs
+    public class CancellationSpecs
     {
         [Fact]
         public async Task Command_can_perform_additional_cleanup_if_cancellation_is_requested()
@@ -22,22 +22,19 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut, cancellationToken: cts.Token);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CancellableCommand))
+                .AddCommand<CancellableCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
             cts.CancelAfter(TimeSpan.FromSeconds(0.2));
 
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"cmd"});
-                new[] {"cancel"},
-                new Dictionary<string, string>());
-
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().NotBe(0);
-            stdOutData.Should().Be("Cancellation requested");
+            stdOutData.Should().Be(CancellableCommand.CancellationOutputText);
         }
     }
 }

CliFx.Tests/CliFx.Tests.csproj

@@ -19,6 +19,7 @@
     <PackageReference Include="FluentAssertions" Version="5.10.2" />
     <PackageReference Include="GitHubActionsTestLogger" Version="1.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.5.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" />
     <PackageReference Include="coverlet.msbuild" Version="2.8.0" PrivateAssets="all" />

CliFx.Tests/Commands/CancellableCommand.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class CancellableCommand : ICommand
+    {
+        public const string CompletionOutputText = "Finished";
+        public const string CancellationOutputText = "Canceled";
+
+        public async ValueTask ExecuteAsync(IConsole console)
+        {
+            try
+            {
+                await Task.Delay(
+                    TimeSpan.FromSeconds(3),
+                    console.GetCancellationToken()
+                );
+
+                console.Output.WriteLine(CompletionOutputText);
+            }
+            catch (OperationCanceledException)
+            {
+                console.Output.WriteLine(CancellationOutputText);
+                throw;
+            }
+        }
+    }
+}

CliFx.Tests/Commands/CommandExceptionCommand.cs

@@ -0,0 +1,21 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Exceptions;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class CommandExceptionCommand : ICommand
+    {
+        [CommandOption("code", 'c')]
+        public int ExitCode { get; set; } = 133;
+
+        [CommandOption("msg", 'm')]
+        public string? Message { get; set; }
+
+        [CommandOption("show-help")]
+        public bool ShowHelp { get; set; }
+
+        public ValueTask ExecuteAsync(IConsole console) => throw new CommandException(Message, ExitCode, ShowHelp);
+    }
+}

CliFx.Tests/Commands/DefaultCommand.cs

@@ -0,0 +1,17 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command(Description = nameof(DefaultCommand))]
+    public class DefaultCommand : ICommand
+    {
+        public const string ExpectedOutputText = nameof(DefaultCommand);
+
+        public ValueTask ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(ExpectedOutputText);
+            return default;
+        }
+    }
+}

CliFx.Tests/Commands/GenericExceptionCommand.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class GenericExceptionCommand : ICommand
+    {
+        [CommandOption("msg", 'm')]
+        public string? Message { get; set; }
+
+        public ValueTask ExecuteAsync(IConsole console) => throw new Exception(Message);
+    }
+}

CliFx.Tests/Commands/Invalid/ConflictWithHelpOptionCommand.cs

@@ -0,0 +1,11 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class ConflictWithHelpOptionCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("option-h", 'h')]
+        public string? OptionH { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/ConflictWithVersionOptionCommand.cs

@@ -0,0 +1,12 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    // Must be default because version option is available only on default commands
+    [Command]
+    public class ConflictWithVersionOptionCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("version")]
+        public string? Version { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/DuplicateOptionEnvironmentVariableNamesCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class DuplicateOptionEnvironmentVariableNamesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("option-a", EnvironmentVariableName = "ENV_VAR")]
+        public string? OptionA { get; set; }
+
+        [CommandOption("option-b", EnvironmentVariableName = "ENV_VAR")]
+        public string? OptionB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/DuplicateOptionNamesCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class DuplicateOptionNamesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("fruits")]
+        public string? Apples { get; set; }
+
+        [CommandOption("fruits")]
+        public string? Oranges { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/DuplicateOptionShortNamesCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class DuplicateOptionShortNamesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption('x')]
+        public string? OptionA { get; set; }
+
+        [CommandOption('x')]
+        public string? OptionB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/DuplicateParameterNameCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class DuplicateParameterNameCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(0, Name = "param")]
+        public string? ParamA { get; set; }
+
+        [CommandParameter(1, Name = "param")]
+        public string? ParamB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/DuplicateParameterOrderCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class DuplicateParameterOrderCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(13)]
+        public string? ParamA { get; set; }
+
+        [CommandParameter(13)]
+        public string? ParamB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/EmptyOptionNameCommand.cs

@@ -0,0 +1,11 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class EmptyOptionNameCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("")]
+        public string? Apples { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/MultipleNonScalarParametersCommand.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class MultipleNonScalarParametersCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(0)]
+        public IReadOnlyList<string>? ParamA { get; set; }
+
+        [CommandParameter(1)]
+        public IReadOnlyList<string>? ParamB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/NonAnnotatedCommand.cs

@@ -0,0 +1,6 @@
+namespace CliFx.Tests.Commands.Invalid
+{
+    public class NonAnnotatedCommand : SelfSerializeCommandBase
+    {
+    }
+}

CliFx.Tests/Commands/Invalid/NonImplementedCommand.cs

@@ -0,0 +1,9 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command]
+    public class NonImplementedCommand
+    {
+    }
+}

CliFx.Tests/Commands/Invalid/NonLastNonScalarParameterCommand.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class NonLastNonScalarParameterCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(0)]
+        public IReadOnlyList<string>? ParamA { get; set; }
+
+        [CommandParameter(1)]
+        public string? ParamB { get; set; }
+    }
+}

CliFx.Tests/Commands/Invalid/OtherDefaultCommand.cs

@@ -0,0 +1,9 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command]
+    public class OtherDefaultCommand : SelfSerializeCommandBase
+    {
+    }
+}

CliFx.Tests/Commands/Invalid/SingleCharacterOptionNameCommand.cs

@@ -0,0 +1,11 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands.Invalid
+{
+    [Command("cmd")]
+    public class SingleCharacterOptionNameCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("a")]
+        public string? Apples { get; set; }
+    }
+}

CliFx.Tests/Commands/NamedCommand.cs

@@ -0,0 +1,17 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("named", Description = nameof(NamedCommand))]
+    public class NamedCommand : ICommand
+    {
+        public const string ExpectedOutputText = nameof(NamedCommand);
+
+        public ValueTask ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(ExpectedOutputText);
+            return default;
+        }
+    }
+}

CliFx.Tests/Commands/NamedSubCommand.cs

@@ -0,0 +1,17 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("named sub", Description = nameof(NamedSubCommand))]
+    public class NamedSubCommand : ICommand
+    {
+        public const string ExpectedOutputText = nameof(NamedSubCommand);
+
+        public ValueTask ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(ExpectedOutputText);
+            return default;
+        }
+    }
+}

CliFx.Tests/Commands/SelfSerializeCommandBase.cs

@@ -0,0 +1,14 @@
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+
+namespace CliFx.Tests.Commands
+{
+    public abstract class SelfSerializeCommandBase : ICommand
+    {
+        public ValueTask ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(JsonConvert.SerializeObject(this));
+            return default;
+        }
+    }
+}

CliFx.Tests/Commands/SupportedArgumentTypesCommand.cs

@@ -0,0 +1,155 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using CliFx.Attributes;
+using Newtonsoft.Json;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public partial class SupportedArgumentTypesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("obj")]
+        public object? Object { get; set; } = 42;
+
+        [CommandOption("str")]
+        public string? String { get; set; } = "foo bar";
+
+        [CommandOption("bool")]
+        public bool Bool { get; set; }
+
+        [CommandOption("char")]
+        public char Char { get; set; }
+
+        [CommandOption("sbyte")]
+        public sbyte Sbyte { get; set; }
+
+        [CommandOption("byte")]
+        public byte Byte { get; set; }
+
+        [CommandOption("short")]
+        public short Short { get; set; }
+
+        [CommandOption("ushort")]
+        public ushort Ushort { get; set; }
+
+        [CommandOption("int")]
+        public int Int { get; set; }
+
+        [CommandOption("uint")]
+        public uint Uint { get; set; }
+
+        [CommandOption("long")]
+        public long Long { get; set; }
+
+        [CommandOption("ulong")]
+        public ulong Ulong { get; set; }
+
+        [CommandOption("float")]
+        public float Float { get; set; }
+
+        [CommandOption("double")]
+        public double Double { get; set; }
+
+        [CommandOption("decimal")]
+        public decimal Decimal { get; set; }
+
+        [CommandOption("datetime")]
+        public DateTime DateTime { get; set; }
+
+        [CommandOption("datetime-offset")]
+        public DateTimeOffset DateTimeOffset { get; set; }
+
+        [CommandOption("timespan")]
+        public TimeSpan TimeSpan { get; set; }
+
+        [CommandOption("enum")]
+        public CustomEnum Enum { get; set; }
+
+        [CommandOption("int-nullable")]
+        public int? IntNullable { get; set; }
+
+        [CommandOption("enum-nullable")]
+        public CustomEnum? EnumNullable { get; set; }
+
+        [CommandOption("timespan-nullable")]
+        public TimeSpan? TimeSpanNullable { get; set; }
+
+        [CommandOption("str-constructible")]
+        public CustomStringConstructible? StringConstructible { get; set; }
+
+        [CommandOption("str-parseable")]
+        public CustomStringParseable? StringParseable { get; set; }
+
+        [CommandOption("str-parseable-format")]
+        public CustomStringParseableWithFormatProvider? StringParseableWithFormatProvider { get; set; }
+
+        [CommandOption("obj-array")]
+        public object[]? ObjectArray { get; set; }
+
+        [CommandOption("str-array")]
+        public string[]? StringArray { get; set; }
+
+        [CommandOption("int-array")]
+        public int[]? IntArray { get; set; }
+
+        [CommandOption("enum-array")]
+        public CustomEnum[]? EnumArray { get; set; }
+
+        [CommandOption("int-nullable-array")]
+        public int?[]? IntNullableArray { get; set; }
+
+        [CommandOption("str-constructible-array")]
+        public CustomStringConstructible[]? StringConstructibleArray { get; set; }
+
+        [CommandOption("str-enumerable")]
+        public IEnumerable<string>? StringEnumerable { get; set; }
+
+        [CommandOption("str-read-only-list")]
+        public IReadOnlyList<string>? StringReadOnlyList { get; set; }
+
+        [CommandOption("str-list")]
+        public List<string>? StringList { get; set; }
+
+        [CommandOption("str-set")]
+        public HashSet<string>? StringHashSet { get; set; }
+    }
+
+    public partial class SupportedArgumentTypesCommand
+    {
+        public enum CustomEnum
+        {
+            Value1 = 1,
+            Value2 = 2,
+            Value3 = 3
+        }
+
+        public class CustomStringConstructible
+        {
+            public string Value { get; }
+
+            public CustomStringConstructible(string value) => Value = value;
+        }
+
+        public class CustomStringParseable
+        {
+            public string Value { get; }
+
+            [JsonConstructor]
+            private CustomStringParseable(string value) => Value = value;
+
+            public static CustomStringParseable Parse(string value) => new CustomStringParseable(value);
+        }
+
+        public class CustomStringParseableWithFormatProvider
+        {
+            public string Value { get; }
+
+            [JsonConstructor]
+            private CustomStringParseableWithFormatProvider(string value) => Value = value;
+
+            public static CustomStringParseableWithFormatProvider Parse(string value, IFormatProvider formatProvider) =>
+                new CustomStringParseableWithFormatProvider(value + " " + formatProvider);
+        }
+    }
+}

CliFx.Tests/Commands/UnsupportedArgumentTypesCommand.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public partial class UnsupportedArgumentTypesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("str-non-initializable")]
+        public CustomType? StringNonInitializable { get; set; }
+
+        [CommandOption("str-enumerable-non-initializable")]
+        public CustomEnumerable<string>? StringEnumerableNonInitializable { get; set; }
+    }
+
+    public partial class UnsupportedArgumentTypesCommand
+    {
+        public class CustomType
+        {
+        }
+
+        public class CustomEnumerable<T> : IEnumerable<T>
+        {
+            public IEnumerator<T> GetEnumerator() => ((IEnumerable<T>) Array.Empty<T>()).GetEnumerator();
+
+            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+        }
+    }
+}

CliFx.Tests/Commands/WithDefaultValuesCommand.cs

@@ -0,0 +1,44 @@
+using System;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithDefaultValuesCommand : SelfSerializeCommandBase
+    {
+        public enum CustomEnum { Value1, Value2, Value3 };
+
+        [CommandOption("obj")]
+        public object? Object { get; set; } = 42;
+
+        [CommandOption("str")]
+        public string? String { get; set; } = "foo";
+
+        [CommandOption("str-empty")]
+        public string StringEmpty { get; set; } = "";
+
+        [CommandOption("str-array")]
+        public string[]? StringArray { get; set; } = { "foo", "bar", "baz" };
+
+        [CommandOption("bool")]
+        public bool Bool { get; set; } = true;
+
+        [CommandOption("char")]
+        public char Char { get; set; } = 't';
+
+        [CommandOption("int")]
+        public int Int { get; set; } = 1337;
+
+        [CommandOption("int-nullable")]
+        public int? IntNullable { get; set; } = 1337;
+
+        [CommandOption("int-array")]
+        public int[]? IntArray { get; set; } = { 1, 2, 3 };
+
+        [CommandOption("timespan")]
+        public TimeSpan TimeSpan { get; set; } = TimeSpan.FromMinutes(123);
+
+        [CommandOption("enum")]
+        public CustomEnum Enum { get; set; } = CustomEnum.Value2;
+    }
+}

CliFx.Tests/Commands/WithDependenciesCommand.cs

@@ -0,0 +1,28 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithDependenciesCommand : ICommand
+    {
+        public class DependencyA
+        {
+        }
+
+        public class DependencyB
+        {
+        }
+
+        private readonly DependencyA _dependencyA;
+        private readonly DependencyB _dependencyB;
+
+        public WithDependenciesCommand(DependencyA dependencyA, DependencyB dependencyB)
+        {
+            _dependencyA = dependencyA;
+            _dependencyB = dependencyB;
+        }
+
+        public ValueTask ExecuteAsync(IConsole console) => default;
+    }
+}

CliFx.Tests/Commands/WithEnumArgumentsCommand.cs

@@ -0,0 +1,19 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithEnumArgumentsCommand : SelfSerializeCommandBase
+    {
+        public enum CustomEnum { Value1, Value2, Value3 };
+
+        [CommandParameter(0, Name = "enum")]
+        public CustomEnum EnumParameter { get; set; }
+
+        [CommandOption("enum")]
+        public CustomEnum? EnumOption { get; set; }
+
+        [CommandOption("required-enum", IsRequired = true)]
+        public CustomEnum RequiredEnumOption { get; set; }
+    }
+}

CliFx.Tests/Commands/WithEnvironmentVariablesCommand.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithEnvironmentVariablesCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("opt-a", 'a', EnvironmentVariableName = "ENV_OPT_A")]
+        public string? OptA { get; set; }
+
+        [CommandOption("opt-b", 'b', EnvironmentVariableName = "ENV_OPT_B")]
+        public IReadOnlyList<string>? OptB { get; set; }
+    }
+}

CliFx.Tests/Commands/WithParametersCommand.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithParametersCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(0)]
+        public string? ParamA { get; set; }
+
+        [CommandParameter(1)]
+        public int? ParamB { get; set; }
+
+        [CommandParameter(2)]
+        public IReadOnlyList<string>? ParamC { get; set; }
+    }
+}

CliFx.Tests/Commands/WithRequiredOptionsCommand.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithRequiredOptionsCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("opt-a", 'a', IsRequired = true)]
+        public string? OptA { get; set; }
+
+        [CommandOption("opt-b", 'b')]
+        public int? OptB { get; set; }
+
+        [CommandOption("opt-c", 'c', IsRequired = true)]
+        public IReadOnlyList<char>? OptC { get; set; }
+    }
+}

CliFx.Tests/Commands/WithSingleParameterCommand.cs

@@ -0,0 +1,11 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithSingleParameterCommand : SelfSerializeCommandBase
+    {
+        [CommandParameter(0)]
+        public string? ParamA { get; set; }
+    }
+}

CliFx.Tests/Commands/WithSingleRequiredOptionCommand.cs

@@ -0,0 +1,14 @@
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithSingleRequiredOptionCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("opt-a")]
+        public string? OptA { get; set; }
+
+        [CommandOption("opt-b", IsRequired = true)]
+        public string? OptB { get; set; }
+    }
+}

CliFx.Tests/Commands/WithStringArrayOptionCommand.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Commands
+{
+    [Command("cmd")]
+    public class WithStringArrayOptionCommand : SelfSerializeCommandBase
+    {
+        [CommandOption("opt", 'o')]
+        public IReadOnlyList<string>? Opt { get; set; }
+    }
+}

CliFx.Tests/ConsoleSpecs.cs

@@ -38,7 +38,8 @@ namespace CliFx.Tests
             var console = new VirtualConsole(
                 input: stdIn,
                 output: stdOut,
-                error: stdErr);
+                error: stdErr
+            );
 
             // Act
             console.Output.Write("output");

CliFx.Tests/DependencyInjectionSpecs.Commands.cs

@@ -1,37 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class DependencyInjectionSpecs
-    {
-        [Command]
-        private class WithoutDependenciesCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        private class DependencyA
-        {
-        }
-
-        private class DependencyB
-        {
-        }
-
-        [Command]
-        private class WithDependenciesCommand : ICommand
-        {
-            private readonly DependencyA _dependencyA;
-            private readonly DependencyB _dependencyB;
-
-            public WithDependenciesCommand(DependencyA dependencyA, DependencyB dependencyB)
-            {
-                _dependencyA = dependencyA;
-                _dependencyB = dependencyB;
-            }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/DependencyInjectionSpecs.cs

@@ -1,11 +1,12 @@
 using CliFx.Exceptions;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class DependencyInjectionSpecs
+    public class DependencyInjectionSpecs
     {
         private readonly ITestOutputHelper _output;
 
@@ -18,10 +19,10 @@ namespace CliFx.Tests
             var activator = new DefaultTypeActivator();
 
             // Act
-            var obj = activator.CreateInstance(typeof(WithoutDependenciesCommand));
+            var obj = activator.CreateInstance(typeof(DefaultCommand));
 
             // Assert
-            obj.Should().BeOfType<WithoutDependenciesCommand>();
+            obj.Should().BeOfType<DefaultCommand>();
         }
 
         [Fact]
@@ -40,7 +41,10 @@ namespace CliFx.Tests
         {
             // Arrange
             var activator = new DelegateTypeActivator(_ =>
-                new WithDependenciesCommand(new DependencyA(), new DependencyB()));
+                new WithDependenciesCommand(
+                    new WithDependenciesCommand.DependencyA(),
+                    new WithDependenciesCommand.DependencyB())
+            );
 
             // Act
             var obj = activator.CreateInstance(typeof(WithDependenciesCommand));

CliFx.Tests/DirectivesSpecs.Commands.cs

@@ -1,14 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class DirectivesSpecs
-    {
-        [Command("cmd")]
-        private class NamedCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/DirectivesSpecs.cs

@@ -1,13 +1,19 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class DirectivesSpecs
+    public class DirectivesSpecs
     {
+        private readonly ITestOutputHelper _output;
+
+        public DirectivesSpecs(ITestOutputHelper output) => _output = output;
+
         [Fact]
         public async Task Preview_directive_can_be_specified_to_print_provided_arguments_as_they_were_parsed()
         {
@@ -16,21 +22,23 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(NamedCommand))
+                .AddCommand<NamedCommand>()
                 .UseConsole(console)
                 .AllowPreviewMode()
                 .Build();
 
             // Act
             var exitCode = await application.RunAsync(
-                new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
+                new[] {"[preview]", "named", "param", "-abc", "--option", "foo"},
                 new Dictionary<string, string>());
 
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().Be(0);
-            stdOutData.Should().ContainAll("cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]");
+            stdOutData.Should().ContainAll("named", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]");
+
+            _output.WriteLine(stdOutData);
         }
     }
 }

CliFx.Tests/EnvironmentVariablesSpecs.Commands.cs

@@ -1,27 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class EnvironmentVariablesSpecs
-    {
-        [Command]
-        private class EnvironmentVariableCollectionCommand : ICommand
-        {
-            [CommandOption("opt", EnvironmentVariableName = "ENV_OPT")]
-            public IReadOnlyList<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class EnvironmentVariableCommand : ICommand
-        {
-            [CommandOption("opt", EnvironmentVariableName = "ENV_OPT")]
-            public string? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/EnvironmentVariablesSpecs.cs

@@ -1,20 +1,20 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
-using CliFx.Domain;
+using CliFx.Tests.Commands;
-using CliFx.Tests.Internal;
 using CliWrap;
 using CliWrap.Buffered;
 using FluentAssertions;
+using Newtonsoft.Json;
 using Xunit;
 
 namespace CliFx.Tests
 {
-    public partial class EnvironmentVariablesSpecs
+    public class EnvironmentVariablesSpecs
     {
         // This test uses a real application to make sure environment variables are actually read correctly
         [Fact]
-        public async Task Option_can_use_a_specific_environment_variable_as_fallback()
+        public async Task Option_can_use_an_environment_variable_as_fallback()
         {
             // Arrange
             var command = Cli.Wrap("dotnet")
@@ -32,7 +32,7 @@ namespace CliFx.Tests
 
         // This test uses a real application to make sure environment variables are actually read correctly
         [Fact]
-        public async Task Option_only_uses_environment_variable_as_fallback_if_the_value_was_not_directly_provided()
+        public async Task Option_only_uses_an_environment_variable_as_fallback_if_the_value_is_not_directly_provided()
         {
             // Arrange
             var command = Cli.Wrap("dotnet")
@@ -51,65 +51,97 @@ namespace CliFx.Tests
         }
 
         [Fact]
-        public void Option_of_non_scalar_type_can_take_multiple_separated_values_from_an_environment_variable()
+        public async Task Option_only_uses_an_environment_variable_as_fallback_if_the_name_matches_case_sensitively()
         {
-            // Arrange
+            await using var stdOut = new MemoryStream();
-            var input = CommandInput.Empty;
+            var console = new VirtualConsole(output: stdOut);
-            var envVars = new Dictionary<string, string>
+
-            {
+            var application = new CliApplicationBuilder()
-                ["ENV_OPT"] = $"foo{Path.PathSeparator}bar"
+                .AddCommand<WithEnvironmentVariablesCommand>()
-            };
+                .UseConsole(console)
+                .Build();
 
             // Act
-            var instance = CommandHelper.ResolveCommand<EnvironmentVariableCollectionCommand>(input, envVars);
+            var exitCode = await application.RunAsync(
+                new[] {"cmd"},
+                new Dictionary<string, string>
+                {
+                    ["ENV_opt_A"] = "incorrect",
+                    ["ENV_OPT_A"] = "correct"
+                }
+            );
+
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+            var commandInstance = JsonConvert.DeserializeObject<WithEnvironmentVariablesCommand>(stdOutData);
 
             // Assert
-            instance.Should().BeEquivalentTo(new EnvironmentVariableCollectionCommand
+            exitCode.Should().Be(0);
+            commandInstance.Should().BeEquivalentTo(new WithEnvironmentVariablesCommand
             {
-                Option = new[] {"foo", "bar"}
+                OptA = "correct"
             });
         }
 
         [Fact]
-        public void Option_of_scalar_type_can_only_take_a_single_value_from_an_environment_variable_even_if_it_contains_separators()
+        public async Task Option_of_non_scalar_type_can_use_an_environment_variable_as_fallback_and_extract_multiple_values()
         {
-            // Arrange
+            await using var stdOut = new MemoryStream();
-            var input = CommandInput.Empty;
+            var console = new VirtualConsole(output: stdOut);
-            var envVars = new Dictionary<string, string>
+
-            {
+            var application = new CliApplicationBuilder()
-                ["ENV_OPT"] = $"foo{Path.PathSeparator}bar"
+                .AddCommand<WithEnvironmentVariablesCommand>()
-            };
+                .UseConsole(console)
+                .Build();
 
             // Act
-            var instance = CommandHelper.ResolveCommand<EnvironmentVariableCommand>(input, envVars);
+            var exitCode = await application.RunAsync(
+                new[] {"cmd"},
+                new Dictionary<string, string>
+                {
+                    ["ENV_OPT_B"] = $"foo{Path.PathSeparator}bar"
+                }
+            );
+
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+            var commandInstance = JsonConvert.DeserializeObject<WithEnvironmentVariablesCommand>(stdOutData);
 
             // Assert
-            instance.Should().BeEquivalentTo(new EnvironmentVariableCommand
+            exitCode.Should().Be(0);
+            commandInstance.Should().BeEquivalentTo(new WithEnvironmentVariablesCommand
             {
-                Option = $"foo{Path.PathSeparator}bar"
+                OptB = new[] {"foo", "bar"}
             });
         }
-        
+
         [Fact]
-        public void Option_can_use_a_specific_environment_variable_as_fallback_while_respecting_case()
+        public async Task Option_of_scalar_type_can_use_an_environment_variable_as_fallback_regardless_of_separators()
         {
-            // Arrange
+            await using var stdOut = new MemoryStream();
-            const string expected = "foobar";
+            var console = new VirtualConsole(output: stdOut);
-            var input = CommandInput.Empty;
+
-            var envVars = new Dictionary<string, string>
+            var application = new CliApplicationBuilder()
-            {
+                .AddCommand<WithEnvironmentVariablesCommand>()
-                ["ENV_OPT"] = expected,
+                .UseConsole(console)
-                ["env_opt"] = "2"
+                .Build();
-            };
 
             // Act
-            var instance = CommandHelper.ResolveCommand<EnvironmentVariableCommand>(input, envVars);
+            var exitCode = await application.RunAsync(
+                new[] {"cmd"},
+                new Dictionary<string, string>
+                {
+                    ["ENV_OPT_A"] = $"foo{Path.PathSeparator}bar"
+                }
+            );
+
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+            var commandInstance = JsonConvert.DeserializeObject<WithEnvironmentVariablesCommand>(stdOutData);
 
             // Assert
-            instance.Should().BeEquivalentTo(new EnvironmentVariableCommand
+            exitCode.Should().Be(0);
+            commandInstance.Should().BeEquivalentTo(new WithEnvironmentVariablesCommand
             {
-                Option = expected
+                OptA = $"foo{Path.PathSeparator}bar"
             });
         }
     }
-}
+}

CliFx.Tests/ErrorReportingSpecs.Commands.cs

@@ -1,34 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Exceptions;
-
-namespace CliFx.Tests
-{
-    public partial class ErrorReportingSpecs
-    {
-        [Command("exc")]
-        private class GenericExceptionCommand : ICommand
-        {
-            [CommandOption("msg", 'm')]
-            public string? Message { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => throw new Exception(Message);
-        }
-
-        [Command("exc")]
-        private class CommandExceptionCommand : ICommand
-        {
-            [CommandOption("code", 'c')]
-            public int ExitCode { get; set; } = 133;
-
-            [CommandOption("msg", 'm')]
-            public string? Message { get; set; }
-
-            [CommandOption("show-help")]
-            public bool ShowHelp { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => throw new CommandException(Message, ExitCode, ShowHelp);
-        }
-    }
-}

CliFx.Tests/ErrorReportingSpecs.cs

@@ -1,13 +1,13 @@
-using System.Collections.Generic;
+using System.IO;
-using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class ErrorReportingSpecs
+    public class ErrorReportingSpecs
     {
         private readonly ITestOutputHelper _output;
 
@@ -17,28 +17,32 @@ namespace CliFx.Tests
         public async Task Command_may_throw_a_generic_exception_which_exits_and_prints_error_message_and_stack_trace()
         {
             // Arrange
+            await using var stdOut = new MemoryStream();
             await using var stdErr = new MemoryStream();
-            var console = new VirtualConsole(error: stdErr);
+
+            var console = new VirtualConsole(output: stdOut, error: stdErr);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(GenericExceptionCommand))
+                .AddCommand<GenericExceptionCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"cmd", "-m", "Kaput"});
-                new[] {"exc", "-m", "Kaput"},
-                new Dictionary<string, string>());
 
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
             var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().NotBe(0);
+            stdOutData.Should().BeEmpty();
             stdErrData.Should().ContainAll(
                 "System.Exception:",
                 "Kaput", "at",
-                "CliFx.Tests");
+                "CliFx.Tests"
+            );
 
+            _output.WriteLine(stdOutData);
             _output.WriteLine(stdErrData);
         }
 
@@ -46,25 +50,28 @@ namespace CliFx.Tests
         public async Task Command_may_throw_a_specialized_exception_which_exits_with_custom_code_and_prints_minimal_error_details()
         {
             // Arrange
+            await using var stdOut = new MemoryStream();
             await using var stdErr = new MemoryStream();
-            var console = new VirtualConsole(error: stdErr);
+
+            var console = new VirtualConsole(output: stdOut, error: stdErr);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CommandExceptionCommand))
+                .AddCommand<CommandExceptionCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"cmd", "-m", "Kaput", "-c", "69"});
-                new[] {"exc", "-m", "Kaput", "-c", "69"},
-                new Dictionary<string, string>());
 
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
             var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().Be(69);
+            stdOutData.Should().BeEmpty();
             stdErrData.Should().Be("Kaput");
 
+            _output.WriteLine(stdOutData);
             _output.WriteLine(stdErrData);
         }
 
@@ -72,28 +79,32 @@ namespace CliFx.Tests
         public async Task Command_may_throw_a_specialized_exception_without_error_message_which_exits_and_prints_full_error_details()
         {
             // Arrange
+            await using var stdOut = new MemoryStream();
             await using var stdErr = new MemoryStream();
-            var console = new VirtualConsole(error: stdErr);
+
+            var console = new VirtualConsole(output: stdOut, error: stdErr);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CommandExceptionCommand))
+                .AddCommand<CommandExceptionCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"cmd"});
-                new[] {"exc"},
-                new Dictionary<string, string>());
 
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
             var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().NotBe(0);
+            stdOutData.Should().BeEmpty();
             stdErrData.Should().ContainAll(
                 "CliFx.Exceptions.CommandException:",
                 "at",
-                "CliFx.Tests");
+                "CliFx.Tests"
+            );
 
+            _output.WriteLine(stdOutData);
             _output.WriteLine(stdErrData);
         }
 
@@ -107,30 +118,27 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut, error: stdErr);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CommandExceptionCommand))
+                .AddCommand<CommandExceptionCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"cmd", "-m", "Kaput", "--show-help"});
-                new[] {"exc", "-m", "Kaput", "--show-help"},
-                new Dictionary<string, string>());
 
-            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().NotBe(0);
-            stdErrData.Should().Be("Kaput");
-
             stdOutData.Should().ContainAll(
                 "Usage",
                 "Options",
-                "-h|--help", "Shows help text."
+                "-h|--help"
             );
+            stdErrData.Should().Be("Kaput");
 
-            _output.WriteLine(stdErrData);
             _output.WriteLine(stdOutData);
+            _output.WriteLine(stdErrData);
         }
 
         [Fact]
@@ -139,34 +147,31 @@ namespace CliFx.Tests
             // Arrange
             await using var stdOut = new MemoryStream();
             await using var stdErr = new MemoryStream();
+
             var console = new VirtualConsole(output: stdOut, error: stdErr);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CommandExceptionCommand))
+                .AddCommand<DefaultCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"not-a-valid-command", "-r", "foo"});
-                new[] {"not-a-valid-command", "-r", "foo"},
-                new Dictionary<string, string>());
 
-            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().NotBe(0);
-            stdErrData.Should().NotBeNullOrWhiteSpace();
-
             stdOutData.Should().ContainAll(
                 "Usage",
-                "[command]",
                 "Options",
-                "-h|--help", "Shows help text."
+                "-h|--help"
             );
+            stdErrData.Should().NotBeNullOrWhiteSpace();
 
-            _output.WriteLine(stdErrData);
             _output.WriteLine(stdOutData);
+            _output.WriteLine(stdErrData);
         }
     }
 }

CliFx.Tests/HelpTextSpecs.Commands.cs

@@ -1,155 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class HelpTextSpecs
-    {
-        [Command(Description = "DefaultCommand description.")]
-        private class DefaultCommand : ICommand
-        {
-            [CommandOption("option-a", 'a', Description = "OptionA description.")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", 'b', Description = "OptionB description.")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd", Description = "NamedCommand description.")]
-        private class NamedCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param-a", Description = "ParameterA description.")]
-            public string? ParameterA { get; set; }
-
-            [CommandOption("option-c", 'c', Description = "OptionC description.")]
-            public string? OptionC { get; set; }
-
-            [CommandOption("option-d", 'd', Description = "OptionD description.")]
-            public string? OptionD { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd sub", Description = "NamedSubCommand description.")]
-        private class NamedSubCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param-b", Description = "ParameterB description.")]
-            public string? ParameterB { get; set; }
-
-            [CommandParameter(1, Name = "param-c", Description = "ParameterC description.")]
-            public string? ParameterC { get; set; }
-
-            [CommandOption("option-e", 'e', Description = "OptionE description.")]
-            public string? OptionE { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-params")]
-        private class ParametersCommand : ICommand
-        {
-            [CommandParameter(0, Name = "first")]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(10)]
-            public int? ParameterB { get; set; }
-
-            [CommandParameter(20, Description = "A list of numbers", Name = "third list")]
-            public IEnumerable<int>? ParameterC { get; set; }
-
-            [CommandOption("option", 'o')]
-            public string? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-req-opts")]
-        private class RequiredOptionsCommand : ICommand
-        {
-            [CommandOption("option-a", 'a', IsRequired = true)]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", 'b', IsRequired = true)]
-            public IEnumerable<int>? OptionB { get; set; }
-
-            [CommandOption("option-c", 'c')]
-            public string? OptionC { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-enum-args")]
-        private class EnumArgumentsCommand : ICommand
-        {
-            public enum CustomEnum { Value1, Value2, Value3 };
-
-            [CommandParameter(0, Name = "value", Description = "Enum parameter.")]
-            public CustomEnum ParamA { get; set; }
-
-            [CommandOption("value", Description = "Enum option.", IsRequired = true)]
-            public CustomEnum OptionA { get; set; } = CustomEnum.Value1;
-
-            [CommandOption("nullable-value", Description = "Nullable enum option.")]
-            public CustomEnum? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-env-vars")]
-        private class EnvironmentVariableCommand : ICommand
-        {
-            [CommandOption("option-a", 'a', IsRequired = true, EnvironmentVariableName = "ENV_OPT_A")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", 'b', EnvironmentVariableName = "ENV_OPT_B")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-defaults")]
-        private class ArgumentsWithDefaultValuesCommand : ICommand
-        {
-            public enum CustomEnum { Value1, Value2, Value3 };
-
-            [CommandOption(nameof(Object))]
-            public object? Object { get; set; } = 42;
-
-            [CommandOption(nameof(String))]
-            public string? String { get; set; } = "foo";
-
-            [CommandOption(nameof(EmptyString))]
-            public string EmptyString { get; set; } = "";
-
-            [CommandOption(nameof(Bool))]
-            public bool Bool { get; set; } = true;
-
-            [CommandOption(nameof(Char))]
-            public char Char { get; set; } = 't';
-
-            [CommandOption(nameof(Int))]
-            public int Int { get; set; } = 1337;
-
-            [CommandOption(nameof(TimeSpan))]
-            public TimeSpan TimeSpan { get; set; } = TimeSpan.FromMinutes(123);
-
-            [CommandOption(nameof(Enum))]
-            public CustomEnum Enum { get; set; } = CustomEnum.Value2;
-
-            [CommandOption(nameof(IntNullable))]
-            public int? IntNullable { get; set; } = 1337;
-
-            [CommandOption(nameof(StringArray))]
-            public string[]? StringArray { get; set; } = { "foo", "bar", "baz" };
-
-            [CommandOption(nameof(IntArray))]
-            public int[]? IntArray { get; set; } = { 1, 2, 3 };
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/HelpTextSpecs.cs

@@ -1,189 +1,18 @@
 using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class HelpTextSpecs
+    public class HelpTextSpecs
     {
         private readonly ITestOutputHelper _output;
 
         public HelpTextSpecs(ITestOutputHelper output) => _output = output;
 
-        [Fact]
-        public async Task Version_information_can_be_requested_by_providing_the_version_option_without_other_arguments()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
-                .AddCommand(typeof(NamedCommand))
-                .AddCommand(typeof(NamedSubCommand))
-                .UseVersionText("v6.9")
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            var exitCode = await application.RunAsync(new[] {"--version"});
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            exitCode.Should().Be(0);
-            stdOutData.Should().Be("v6.9");
-
-            _output.WriteLine(stdOutData);
-        }
-
-        [Fact]
-        public async Task Help_text_can_be_requested_by_providing_the_help_option()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
-                .AddCommand(typeof(NamedCommand))
-                .AddCommand(typeof(NamedSubCommand))
-                .UseTitle("AppTitle")
-                .UseVersionText("AppVer")
-                .UseDescription("AppDesc")
-                .UseExecutableName("AppExe")
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            await application.RunAsync(new[] {"--help"});
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            stdOutData.Should().ContainAll(
-                "AppTitle", "AppVer",
-                "AppDesc",
-                "Usage",
-                "AppExe", "[command]", "[options]",
-                "Options",
-                "-a|--option-a", "OptionA description.",
-                "-b|--option-b", "OptionB description.",
-                "-h|--help", "Shows help text.",
-                "--version", "Shows version information.",
-                "Commands",
-                "cmd", "NamedCommand description.",
-                "You can run", "to show help on a specific command."
-            );
-
-            _output.WriteLine(stdOutData);
-        }
-
-        [Fact]
-        public async Task Help_text_can_be_requested_on_a_specific_named_command()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
-                .AddCommand(typeof(NamedCommand))
-                .AddCommand(typeof(NamedSubCommand))
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            await application.RunAsync(new[] {"cmd", "--help"});
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            stdOutData.Should().ContainAll(
-                "Description",
-                "NamedCommand description.",
-                "Usage",
-                "cmd", "[command]", "<param-a>", "[options]",
-                "Parameters",
-                "* param-a", "ParameterA description.",
-                "Options",
-                "-c|--option-c", "OptionC description.",
-                "-d|--option-d", "OptionD description.",
-                "-h|--help", "Shows help text.",
-                "Commands",
-                "sub", "SubCommand description.",
-                "You can run", "to show help on a specific command."
-            );
-
-            _output.WriteLine(stdOutData);
-        }
-
-        [Fact]
-        public async Task Help_text_can_be_requested_on_a_specific_named_sub_command()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
-                .AddCommand(typeof(NamedCommand))
-                .AddCommand(typeof(NamedSubCommand))
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            await application.RunAsync(new[] {"cmd", "sub", "--help"});
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            stdOutData.Should().ContainAll(
-                "Description",
-                "SubCommand description.",
-                "Usage",
-                "cmd sub", "<param-b>", "<param-c>", "[options]",
-                "Parameters",
-                "* param-b", "ParameterB description.",
-                "* param-c", "ParameterC description.",
-                "Options",
-                "-e|--option-e", "OptionE description.",
-                "-h|--help", "Shows help text."
-            );
-
-            _output.WriteLine(stdOutData);
-        }
-
-        [Fact]
-        public async Task Help_text_can_be_requested_without_specifying_command_even_if_default_command_is_not_defined()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(NamedCommand))
-                .AddCommand(typeof(NamedSubCommand))
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            await application.RunAsync(new[] {"--help"});
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            stdOutData.Should().ContainAll(
-                "Usage",
-                "[command]",
-                "Options",
-                "-h|--help", "Shows help text.",
-                "--version", "Shows version information.",
-                "Commands",
-                "cmd", "NamedCommand description.",
-                "You can run", "to show help on a specific command."
-            );
-
-            _output.WriteLine(stdOutData);
-        }
-
         [Fact]
         public async Task Help_text_shows_usage_format_which_lists_all_parameters()
         {
@@ -192,18 +21,19 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(ParametersCommand))
+                .AddCommand<WithParametersCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            await application.RunAsync(new[] {"cmd-with-params", "--help"});
+            var exitCode = await application.RunAsync(new[] {"cmd", "--help"});
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
+            exitCode.Should().Be(0);
             stdOutData.Should().ContainAll(
                 "Usage",
-                "cmd-with-params", "<first>", "<parameterb>", "<third list...>", "[options]"
+                "cmd", "<parama>", "<paramb>", "<paramc...>"
             );
 
             _output.WriteLine(stdOutData);
@@ -217,78 +47,79 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(RequiredOptionsCommand))
+                .AddCommand<WithRequiredOptionsCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            await application.RunAsync(new[] {"cmd-with-req-opts", "--help"});
+            var exitCode = await application.RunAsync(new[] {"cmd", "--help"});
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
+            exitCode.Should().Be(0);
             stdOutData.Should().ContainAll(
                 "Usage",
-                "cmd-with-req-opts", "--option-a <value>", "--option-b <values...>", "[options]",
+                "cmd", "--opt-a <value>", "--opt-c <values...>", "[options]",
                 "Options",
-                "* -a|--option-a",
+                "* -a|--opt-a",
-                "* -b|--option-b",
+                "-b|--opt-b",
-                "-c|--option-c"
+                "* -c|--opt-c"
             );
 
             _output.WriteLine(stdOutData);
         }
 
         [Fact]
-        public async Task Help_text_lists_all_valid_values_for_enum_arguments()
+        public async Task Help_text_shows_all_valid_values_for_enum_arguments()
         {
             // Arrange
             await using var stdOut = new MemoryStream();
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(EnumArgumentsCommand))
+                .AddCommand<WithEnumArgumentsCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            await application.RunAsync(new[] {"cmd-with-enum-args", "--help"});
+            var exitCode = await application.RunAsync(new[] {"cmd", "--help"});
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
+            exitCode.Should().Be(0);
             stdOutData.Should().ContainAll(
-                "Usage",
-                "cmd-with-enum-args", "[options]",
                 "Parameters",
-                "value", "Valid values: \"Value1\", \"Value2\", \"Value3\".",
+                "enum", "Valid values: \"Value1\", \"Value2\", \"Value3\".",
                 "Options",
-                "* --value", "Enum option.", "Valid values: \"Value1\", \"Value2\", \"Value3\".",
+                "--enum", "Valid values: \"Value1\", \"Value2\", \"Value3\".",
-                "--nullable-value", "Nullable enum option.", "Valid values: \"Value1\", \"Value2\", \"Value3\"."
+                "* --required-enum", "Valid values: \"Value1\", \"Value2\", \"Value3\"."
             );
 
             _output.WriteLine(stdOutData);
         }
 
         [Fact]
-        public async Task Help_text_lists_environment_variable_names_for_options_that_have_them_defined()
+        public async Task Help_text_shows_environment_variable_names_for_options_that_have_them_defined()
         {
             // Arrange
             await using var stdOut = new MemoryStream();
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(EnvironmentVariableCommand))
+                .AddCommand<WithEnvironmentVariablesCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            await application.RunAsync(new[] {"cmd-with-env-vars", "--help"});
+            var exitCode = await application.RunAsync(new[] {"cmd", "--help"});
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
+            exitCode.Should().Be(0);
             stdOutData.Should().ContainAll(
                 "Options",
-                "* -a|--option-a", "Environment variable:", "ENV_OPT_A",
+                "-a|--opt-a", "Environment variable:", "ENV_OPT_A",
-                "-b|--option-b", "Environment variable:", "ENV_OPT_B"
+                "-b|--opt-b", "Environment variable:", "ENV_OPT_B"
             );
 
             _output.WriteLine(stdOutData);
@@ -302,30 +133,29 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(ArgumentsWithDefaultValuesCommand))
+                .AddCommand<WithDefaultValuesCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            await application.RunAsync(new[] {"cmd-with-defaults", "--help"});
+            var exitCode = await application.RunAsync(new[] {"cmd", "--help"});
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
+            exitCode.Should().Be(0);
             stdOutData.Should().ContainAll(
-                "Usage",
-                "cmd-with-defaults", "[options]",
                 "Options",
-                "--Object", "Default: \"42\"",
+                "--obj", "Default: \"42\"",
-                "--String", "Default: \"foo\"",
+                "--str", "Default: \"foo\"",
-                "--EmptyString", "Default: \"\"",
+                "--str-empty", "Default: \"\"",
-                "--Bool", "Default: \"True\"",
+                "--str-array", "Default: \"foo\" \"bar\" \"baz\"",
-                "--Char", "Default: \"t\"",
+                "--bool", "Default: \"True\"",
-                "--Int", "Default: \"1337\"",
+                "--char", "Default: \"t\"",
-                "--TimeSpan", "Default: \"02:03:00\"",
+                "--int", "Default: \"1337\"",
-                "--Enum", "Default: \"Value2\"",
+                "--int-nullable", "Default: \"1337\"",
-                "--IntNullable", "Default: \"1337\"",
+                "--int-array", "Default: \"1\" \"2\" \"3\"",
-                "--StringArray", "Default: \"foo\" \"bar\" \"baz\"",
+                "--timespan", "Default: \"02:03:00\"",
-                "--IntArray", "Default: \"1\" \"2\" \"3\""
+                "--enum", "Default: \"Value2\""
             );
 
             _output.WriteLine(stdOutData);

CliFx.Tests/Internal/CommandHelper.cs

@@ -1,23 +0,0 @@
-using System.Collections.Generic;
-using CliFx.Domain;
-
-namespace CliFx.Tests.Internal
-{
-    internal static class CommandHelper
-    {
-        public static TCommand ResolveCommand<TCommand>(CommandInput input, IReadOnlyDictionary<string, string> environmentVariables)
-            where TCommand : ICommand, new()
-        {
-            var schema = CommandSchema.TryResolve(typeof(TCommand))!;
-
-            var instance = new TCommand();
-            schema.Bind(instance, input, environmentVariables);
-
-            return instance;
-        }
-
-        public static TCommand ResolveCommand<TCommand>(CommandInput input)
-            where TCommand : ICommand, new() =>
-            ResolveCommand<TCommand>(input, new Dictionary<string, string>());
-    }
-}

CliFx.Tests/Internal/CommandInputBuilder.cs

@@ -1,45 +0,0 @@
-using System.Collections.Generic;
-using CliFx.Domain;
-
-namespace CliFx.Tests.Internal
-{
-    internal class CommandInputBuilder
-    {
-        private readonly List<CommandDirectiveInput> _directives = new List<CommandDirectiveInput>();
-        private readonly List<CommandParameterInput> _parameters = new List<CommandParameterInput>();
-        private readonly List<CommandOptionInput> _options = new List<CommandOptionInput>();
-
-        private string? _commandName;
-
-        public CommandInputBuilder SetCommandName(string commandName)
-        {
-            _commandName = commandName;
-            return this;
-        }
-
-        public CommandInputBuilder AddDirective(string directive)
-        {
-            _directives.Add(new CommandDirectiveInput(directive));
-            return this;
-        }
-
-        public CommandInputBuilder AddParameter(string parameter)
-        {
-            _parameters.Add(new CommandParameterInput(parameter));
-            return this;
-        }
-
-        public CommandInputBuilder AddOption(string alias, params string[] values)
-        {
-            _options.Add(new CommandOptionInput(alias, values));
-            return this;
-        }
-
-        public CommandInput Build() => new CommandInput(
-            _directives,
-            _commandName,
-            _parameters,
-            _options
-        );
-    }
-}

CliFx.Tests/Internal/TaskExtensions.cs

@@ -1,19 +0,0 @@
-using System;
-using System.Threading.Tasks;
-
-namespace CliFx.Tests.Internal
-{
-    internal static class TaskExtensions
-    {
-        public static async Task IgnoreCancellation(this Task task)
-        {
-            try
-            {
-                await task;
-            }
-            catch (OperationCanceledException)
-            {
-            }
-        }
-    }
-}

CliFx.Tests/RoutingSpecs.Commands.cs

@@ -1,52 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class RoutingSpecs
-    {
-        [Command]
-        private class DefaultCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine("Hello world!");
-                return default;
-            }
-        }
-
-        [Command("concat", Description = "Concatenate strings.")]
-        private class ConcatCommand : ICommand
-        {
-            [CommandOption('i', IsRequired = true, Description = "Input strings.")]
-            public IReadOnlyList<string> Inputs { get; set; } = Array.Empty<string>();
-
-            [CommandOption('s', Description = "String separator.")]
-            public string Separator { get; set; } = "";
-
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine(string.Join(Separator, Inputs));
-                return default;
-            }
-        }
-
-        [Command("div", Description = "Divide one number by another.")]
-        private class DivideCommand : ICommand
-        {
-            [CommandOption("dividend", 'D', IsRequired = true, Description = "The number to divide.")]
-            public double Dividend { get; set; } = 0;
-
-            [CommandOption("divisor", 'd', IsRequired = true, Description = "The number to divide by.")]
-            public double Divisor { get; set; } = 0;
-
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine(Dividend / Divisor);
-                return default;
-            }
-        }
-    }
-}

CliFx.Tests/RoutingSpecs.cs

@@ -1,14 +1,19 @@
 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Commands;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
 namespace CliFx.Tests
 {
-    public partial class RoutingSpecs
+    public class RoutingSpecs
     {
+        private readonly ITestOutputHelper _output;
+
+        public RoutingSpecs(ITestOutputHelper testOutput) => _output = testOutput;
+
         [Fact]
         public async Task Default_command_is_executed_if_provided_arguments_do_not_match_any_named_command()
         {
@@ -17,48 +22,21 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
+                .AddCommand<DefaultCommand>()
-                .AddCommand(typeof(ConcatCommand))
+                .AddCommand<NamedCommand>()
-                .AddCommand(typeof(DivideCommand))
+                .AddCommand<NamedSubCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(Array.Empty<string>());
-                Array.Empty<string>(),
-                new Dictionary<string, string>());
-
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().Be(0);
-            stdOutData.Should().Be("Hello world!");
+            stdOutData.Should().Be(DefaultCommand.ExpectedOutputText);
-        }
 
-        [Fact]
+            _output.WriteLine(stdOutData);
-        public async Task Help_text_is_printed_if_no_arguments_were_provided_and_default_command_is_not_defined()
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(ConcatCommand))
-                .AddCommand(typeof(DivideCommand))
-                .UseConsole(console)
-                .UseDescription("This will be visible in help")
-                .Build();
-
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>());
-
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            exitCode.Should().Be(0);
-            stdOutData.Should().Contain("This will be visible in help");
         }
 
         [Fact]
@@ -69,22 +47,208 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
+                .AddCommand<DefaultCommand>()
-                .AddCommand(typeof(ConcatCommand))
+                .AddCommand<NamedCommand>()
-                .AddCommand(typeof(DivideCommand))
+                .AddCommand<NamedSubCommand>()
                 .UseConsole(console)
                 .Build();
 
             // Act
-            var exitCode = await application.RunAsync(
+            var exitCode = await application.RunAsync(new[] {"named"});
-                new[] {"concat", "-i", "foo", "bar", "-s", ", "},
-                new Dictionary<string, string>());
-
             var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
             // Assert
             exitCode.Should().Be(0);
-            stdOutData.Should().Be("foo, bar");
+            stdOutData.Should().Be(NamedCommand.ExpectedOutputText);
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Specific_named_sub_command_is_executed_if_provided_arguments_match_its_name()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"named", "sub"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().Be(NamedSubCommand.ExpectedOutputText);
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Help_text_is_printed_if_no_arguments_were_provided_and_default_command_is_not_defined()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseConsole(console)
+                .UseDescription("This will be visible in help")
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(Array.Empty<string>());
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().Contain("This will be visible in help");
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Help_text_is_printed_if_provided_arguments_contain_the_help_option()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"--help"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().ContainAll(
+                nameof(DefaultCommand),
+                "Usage"
+            );
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Help_text_is_printed_if_provided_arguments_contain_the_help_option_even_if_default_command_is_not_defined()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseDescription("This will be visible in help")
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"--help"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().Contain("This will be visible in help");
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Help_text_for_a_specific_named_command_is_printed_if_provided_arguments_match_its_name_and_contain_the_help_option()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"named", "--help"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().ContainAll(
+                nameof(NamedCommand),
+                "Usage",
+                "named"
+            );
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Help_text_for_a_specific_named_sub_command_is_printed_if_provided_arguments_match_its_name_and_contain_the_help_option()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"named", "sub", "--help"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().ContainAll(
+                nameof(NamedSubCommand),
+                "Usage",
+                "named", "sub"
+            );
+
+            _output.WriteLine(stdOutData);
+        }
+
+        [Fact]
+        public async Task Version_is_printed_if_the_only_provided_argument_is_the_version_option()
+        {
+            // Arrange
+            await using var stdOut = new MemoryStream();
+            var console = new VirtualConsole(output: stdOut);
+
+            var application = new CliApplicationBuilder()
+                .AddCommand<DefaultCommand>()
+                .AddCommand<NamedCommand>()
+                .AddCommand<NamedSubCommand>()
+                .UseVersionText("v6.9")
+                .UseConsole(console)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(new[] {"--version"});
+            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOutData.Should().Be("v6.9");
+
+            _output.WriteLine(stdOutData);
         }
     }
 }

CliFx/CliApplicationBuilder.cs

@@ -34,6 +34,12 @@ namespace CliFx
             return this;
         }
 
+        /// <summary>
+        /// Adds a command of specified type to the application.
+        /// </summary>
+        public CliApplicationBuilder AddCommand<TCommand>() where TCommand : ICommand =>
+            AddCommand(typeof(TCommand));
+
         /// <summary>
         /// Adds multiple commands to the application.
         /// </summary>

CliFx/CliFx.csproj

@@ -23,15 +23,6 @@
     <Nullable>annotations</Nullable>
   </PropertyGroup>
 
-  <ItemGroup>
-    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
-      <_Parameter1>$(AssemblyName).Tests</_Parameter1>
-    </AssemblyAttribute>
-    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
-      <_Parameter1>$(AssemblyName).Analyzers</_Parameter1>
-    </AssemblyAttribute>
-  </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="all" />

CliFx/Domain/CommandArgumentSchema.cs

@@ -48,7 +48,7 @@ namespace CliFx.Domain
                         ? ConvertScalar(value, nullableUnderlyingType)
                         : null;
 
-                // String-constructable
+                // String-constructible
                 var stringConstructor = targetType.GetConstructor(new[] {typeof(string)});
                 if (stringConstructor != null)
                     return stringConstructor.Invoke(new object[] {value!});
@@ -83,7 +83,7 @@ namespace CliFx.Domain
             if (targetEnumerableType.IsAssignableFrom(arrayType))
                 return array;
 
-            // Constructable from an array
+            // Constructible from an array
             var arrayConstructor = targetEnumerableType.GetConstructor(new[] {arrayType});
             if (arrayConstructor != null)
                 return arrayConstructor.Invoke(new object[] {array});

Readme.md

@@ -573,7 +573,7 @@ public async Task ConcatCommand_Test()
     var console = new VirtualConsole(output: stdOut);
 
     var app = new CliApplicationBuilder()
-        .AddCommand(typeof(ConcatCommand))
+        .AddCommand<ConcatCommand>()
         .UseConsole(console)
         .Build();