Update version

Closes #7
Closes #8

CliFx.Tests.Dummy/CliFx.Tests.Dummy.csproj

@@ -1,14 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <OutputType>Exe</OutputType>
-    <TargetFramework>net46</TargetFramework>
-    <Version>1.2.3.4</Version>
-    <LangVersion>latest</LangVersion>
-  </PropertyGroup>
-
-  <ItemGroup>
-    <ProjectReference Include="..\CliFx\CliFx.csproj" />
-  </ItemGroup>
-
-</Project>

CliFx.Tests.Dummy/Commands/GreeterCommand.cs

@@ -1,31 +0,0 @@
-using System.Text;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests.Dummy.Commands
-{
-    [Command]
-    public class GreeterCommand : ICommand
-    {
-        [CommandOption("target", 't', Description = "Greeting target.")]
-        public string Target { get; set; } = "world";
-
-        [CommandOption('e', Description = "Whether the greeting should be exclaimed.")]
-        public bool IsExclaimed { get; set; }
-
-        public Task ExecuteAsync(IConsole console)
-        {
-            var buffer = new StringBuilder();
-
-            buffer.Append("Hello").Append(' ').Append(Target);
-
-            if (IsExclaimed)
-                buffer.Append('!');
-
-            console.Output.WriteLine(buffer.ToString());
-
-            return Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests.Dummy/Commands/LogCommand.cs

@@ -1,25 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests.Dummy.Commands
-{
-    [Command("log", Description = "Calculate the logarithm of a value.")]
-    public class LogCommand : ICommand
-    {
-        [CommandOption("value", 'v', IsRequired = true, Description = "Value whose logarithm is to be found.")]
-        public double Value { get; set; }
-
-        [CommandOption("base", 'b', Description = "Logarithm base.")]
-        public double Base { get; set; } = 10;
-
-        public Task ExecuteAsync(IConsole console)
-        {
-            var result = Math.Log(Value, Base);
-            console.Output.WriteLine(result);
-
-            return Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests.Dummy/Commands/SumCommand.cs

@@ -1,23 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests.Dummy.Commands
-{
-    [Command("sum", Description = "Calculate the sum of all input values.")]
-    public class SumCommand : ICommand
-    {
-        [CommandOption("values", 'v', IsRequired = true, Description = "Input values.")]
-        public IReadOnlyList<double> Values { get; set; }
-
-        public Task ExecuteAsync(IConsole console)
-        {
-            var result = Values.Sum();
-            console.Output.WriteLine(result);
-
-            return Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests.Dummy/Program.cs

@@ -1,21 +0,0 @@
-using System.Globalization;
-using System.Threading.Tasks;
-
-namespace CliFx.Tests.Dummy
-{
-    public static class Program
-    {
-        public static Task<int> Main(string[] args)
-        {
-            // Set culture to invariant to maintain consistent format because we rely on it in tests
-            CultureInfo.DefaultThreadCurrentCulture = CultureInfo.InvariantCulture;
-            CultureInfo.DefaultThreadCurrentUICulture = CultureInfo.InvariantCulture;
-
-            return new CliApplicationBuilder()
-                .AddCommandsFromThisAssembly()
-                .UseDescription("Dummy program used for E2E tests.")
-                .Build()
-                .RunAsync(args);
-        }
-    }
-}

CliFx.Tests/CliApplicationBuilderTests.cs

@@ -0,0 +1,48 @@
+using System;
+using System.IO;
+using CliFx.Services;
+using CliFx.Tests.TestCommands;
+using NUnit.Framework;
+
+namespace CliFx.Tests
+{
+    [TestFixture]
+    public class CliApplicationBuilderTests
+    {
+        // Make sure all builder methods work
+        [Test]
+        public void All_Smoke_Test()
+        {
+            // Arrange
+            var builder = new CliApplicationBuilder();
+
+            // Act
+            builder
+                .AddCommand(typeof(HelloWorldDefaultCommand))
+                .AddCommandsFrom(typeof(HelloWorldDefaultCommand).Assembly)
+                .AddCommands(new[] {typeof(HelloWorldDefaultCommand)})
+                .AddCommandsFrom(new[] {typeof(HelloWorldDefaultCommand).Assembly})
+                .AddCommandsFromThisAssembly()
+                .AllowDebugMode()
+                .AllowPreviewMode()
+                .UseTitle("test")
+                .UseExecutableName("test")
+                .UseVersionText("test")
+                .UseDescription("test")
+                .UseConsole(new VirtualConsole(TextWriter.Null))
+                .UseCommandFactory(schema => (ICommand) Activator.CreateInstance(schema.Type))
+                .Build();
+        }
+
+        // Make sure builder can produce an application with no parameters specified
+        [Test]
+        public void Build_Test()
+        {
+            // Arrange
+            var builder = new CliApplicationBuilder();
+
+            // Act
+            builder.Build();
+        }
+    }
+}

CliFx.Tests/CliApplicationTests.Commands.cs

@@ -1,53 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Exceptions;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class CliApplicationTests
-    {
-        [Command]
-        private class DefaultCommand : ICommand
-        {
-            public Task ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine("DefaultCommand executed.");
-                return Task.CompletedTask;
-            }
-        }
-
-        [Command("cmd")]
-        private class NamedCommand : ICommand
-        {
-            public Task ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine("NamedCommand executed.");
-                return Task.CompletedTask;
-            }
-        }
-    }
-
-    // Negative
-    public partial class CliApplicationTests
-    {
-        [Command("faulty1")]
-        private class FaultyCommand1 : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => throw new CommandException(150);
-        }
-
-        [Command("faulty2")]
-        private class FaultyCommand2 : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => throw new CommandException("FaultyCommand2 error message.", 150);
-        }
-
-        [Command("faulty3")]
-        private class FaultyCommand3 : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => throw new Exception("FaultyCommand3 error message.");
-        }
-    }
-}

CliFx.Tests/CliApplicationTests.cs

@@ -3,74 +3,119 @@ using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
 using CliFx.Services;
+using CliFx.Tests.TestCommands;
 using FluentAssertions;
 using NUnit.Framework;
 
 namespace CliFx.Tests
 {
     [TestFixture]
-    public partial class CliApplicationTests
+    public class CliApplicationTests
     {
+        private const string TestVersionText = "v1.0";
+
         private static IEnumerable<TestCaseData> GetTestCases_RunAsync()
         {
             yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
+                new[] {typeof(HelloWorldDefaultCommand)},
                 new string[0],
-                "DefaultCommand executed."
+                "Hello world."
             );
             
             yield return new TestCaseData(
-                new[] {typeof(NamedCommand)},
-                new[] {"cmd"},
-                "NamedCommand executed."
-            );
-        }
-
-        private static IEnumerable<TestCaseData> GetTestCases_HelpAndVersion_RunAsync()
-        {
-            yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
-                new string[0]
+                new[] {typeof(ConcatCommand)},
+                new[] {"concat", "-i", "foo", "-i", "bar", "-s", " "},
+                "foo bar"
             );
             
             yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
-                new[] {"-h"}
+                new[] {typeof(ConcatCommand)},
+                new[] {"concat", "-i", "one", "two", "three", "-s", ", "},
+                "one, two, three"
             );
 
             yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
-                new[] {"--help"}
+                new[] {typeof(DivideCommand)},
+                new[] {"div", "-D", "24", "-d", "8"},
+                "3"
             );
 
             yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
-                new[] {"--version"}
+                new[] {typeof(HelloWorldDefaultCommand)},
+                new[] {"--version"},
+                TestVersionText
             );
 
             yield return new TestCaseData(
-                new[] {typeof(NamedCommand)},
-                new string[0]
+                new[] {typeof(ConcatCommand)},
+                new[] {"--version"},
+                TestVersionText
             );
             
             yield return new TestCaseData(
-                new[] {typeof(NamedCommand)},
-                new[] {"cmd", "-h"}
+                new[] {typeof(HelloWorldDefaultCommand)},
+                new[] {"-h"},
+                null
             );
 
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand1)},
-                new[] {"faulty1", "-h"}
+                new[] {typeof(HelloWorldDefaultCommand)},
+                new[] {"--help"},
+                null
             );
             
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand2)},
-                new[] {"faulty2", "-h"}
+                new[] {typeof(ConcatCommand)},
+                new string[0],
+                null
             );
             
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand3)},
-                new[] {"faulty3", "-h"}
+                new[] {typeof(ConcatCommand)},
+                new[] {"-h"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(ConcatCommand)},
+                new[] {"--help"},
+                null
+            );
+            
+            yield return new TestCaseData(
+                new[] {typeof(ConcatCommand)},
+                new[] {"concat", "-h"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(ExceptionCommand)},
+                new[] {"exc", "-h"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(CommandExceptionCommand)},
+                new[] {"exc", "-h"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(ConcatCommand)},
+                new[] {"[preview]"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(ExceptionCommand)},
+                new[] {"exc", "[preview]"},
+                null
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(ConcatCommand)},
+                new[] {"concat", "[preview]", "-o", "value"},
+                null
             );
         }
 
@@ -78,96 +123,107 @@ namespace CliFx.Tests
         {
             yield return new TestCaseData(
                 new Type[0],
-                new string[0]
+                new string[0],
+                null, null
             );
 
             yield return new TestCaseData(
-                new[] {typeof(DefaultCommand)},
-                new[] {"non-existing"}
+                new[] {typeof(ConcatCommand)},
+                new[] {"non-existing"},
+                null, null
             );
 
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand1)},
-                new[] {"faulty1"}
+                new[] {typeof(ExceptionCommand)},
+                new[] {"exc"},
+                null, null
             );
 
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand2)},
-                new[] {"faulty2"}
+                new[] {typeof(CommandExceptionCommand)},
+                new[] {"exc"},
+                null, null
             );
 
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand3)},
-                new[] {"faulty3"}
+                new[] {typeof(CommandExceptionCommand)},
+                new[] {"exc"},
+                null, null
+            );
+         
+            yield return new TestCaseData(
+                new[] {typeof(CommandExceptionCommand)},
+                new[] {"exc", "-m", "foo bar"},
+                "foo bar", null
+            );
+            
+            yield return new TestCaseData(
+                new[] {typeof(CommandExceptionCommand)},
+                new[] {"exc", "-m", "foo bar", "-c", "666"},
+                "foo bar", 666
             );
         }
 
         [Test]
         [TestCaseSource(nameof(GetTestCases_RunAsync))]
-        public async Task RunAsync_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<string> commandLineArguments, string expectedStdOut)
+        public async Task RunAsync_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<string> commandLineArguments,
+            string expectedStdOut = null)
         {
             // Arrange
-            using (var stdout = new StringWriter())
+            using (var stdoutStream = new StringWriter())
             {
-                var console = new VirtualConsole(stdout);
+                var console = new VirtualConsole(stdoutStream);
 
                 var application = new CliApplicationBuilder()
                     .AddCommands(commandTypes)
+                    .UseVersionText(TestVersionText)
                     .UseConsole(console)
                     .Build();
 
                 // Act
                 var exitCode = await application.RunAsync(commandLineArguments);
+                var stdOut = stdoutStream.ToString().Trim();
 
                 // Assert
                 exitCode.Should().Be(0);
-                stdout.ToString().Trim().Should().Be(expectedStdOut);
-            }
-        }
 
-        [Test]
-        [TestCaseSource(nameof(GetTestCases_HelpAndVersion_RunAsync))]
-        public async Task RunAsync_HelpAndVersion_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<string> commandLineArguments)
-        {
-            // Arrange
-            using (var stdout = new StringWriter())
-            {
-                var console = new VirtualConsole(stdout);
-
-                var application = new CliApplicationBuilder()
-                    .AddCommands(commandTypes)
-                    .UseConsole(console)
-                    .Build();
-
-                // Act
-                var exitCode = await application.RunAsync(commandLineArguments);
-
-                // Assert
-                exitCode.Should().Be(0);
-                stdout.ToString().Should().NotBeNullOrWhiteSpace();
+                if (expectedStdOut != null)
+                    stdOut.Should().Be(expectedStdOut);
+                else
+                    stdOut.Should().NotBeNullOrWhiteSpace();
             }
         }
 
         [Test]
         [TestCaseSource(nameof(GetTestCases_RunAsync_Negative))]
-        public async Task RunAsync_Negative_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<string> commandLineArguments)
+        public async Task RunAsync_Negative_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<string> commandLineArguments,
+            string expectedStdErr = null, int? expectedExitCode = null)
         {
             // Arrange
-            using (var stderr = new StringWriter())
+            using (var stderrStream = new StringWriter())
             {
-                var console = new VirtualConsole(TextWriter.Null, stderr);
+                var console = new VirtualConsole(TextWriter.Null, stderrStream);
 
                 var application = new CliApplicationBuilder()
                     .AddCommands(commandTypes)
+                    .UseVersionText(TestVersionText)
                     .UseConsole(console)
                     .Build();
 
                 // Act
                 var exitCode = await application.RunAsync(commandLineArguments);
+                var stderr = stderrStream.ToString().Trim();
 
                 // Assert
+                if (expectedExitCode != null)
+                    exitCode.Should().Be(expectedExitCode);
+                else
                     exitCode.Should().NotBe(0);
-                stderr.ToString().Should().NotBeNullOrWhiteSpace();
+                
+                if (expectedStdErr != null)
+                    stderr.Should().Be(expectedStdErr);
+                else
+                    stderr.Should().NotBeNullOrWhiteSpace();
             }
         }
     }

CliFx.Tests/CliFx.Tests.csproj

@@ -15,7 +15,6 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.2.0" />
     <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="3.14.0" />
-    <PackageReference Include="CliWrap" Version="2.3.1" />
     <PackageReference Include="coverlet.msbuild" Version="2.6.3">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
@@ -23,7 +22,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\CliFx.Tests.Dummy\CliFx.Tests.Dummy.csproj" />
     <ProjectReference Include="..\CliFx\CliFx.csproj" />
   </ItemGroup>
 

CliFx.Tests/CommandFactoryTests.Commands.cs

@@ -1,15 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class CommandFactoryTests
-    {
-        [Command]
-        private class TestCommand : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests/CommandInitializerTests.Commands.cs

@@ -1,21 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class CommandInitializerTests
-    {
-        [Command]
-        private class TestCommand : ICommand
-        {
-            [CommandOption("int", 'i', IsRequired = true)]
-            public int IntOption { get; set; } = 24;
-
-            [CommandOption("str", 's')]
-            public string StringOption { get; set; } = "foo bar";
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests/CommandInitializerTests.cs

@@ -1,96 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using CliFx.Exceptions;
-using CliFx.Models;
-using CliFx.Services;
-using FluentAssertions;
-using NUnit.Framework;
-
-namespace CliFx.Tests
-{
-    [TestFixture]
-    public partial class CommandInitializerTests
-    {
-        private static CommandSchema GetCommandSchema(Type commandType) =>
-            new CommandSchemaResolver().GetCommandSchemas(new[] {commandType}).Single();
-
-        private static IEnumerable<TestCaseData> GetTestCases_InitializeCommand()
-        {
-            yield return new TestCaseData(
-                new TestCommand(),
-                GetCommandSchema(typeof(TestCommand)),
-                new CommandInput(new[]
-                {
-                    new CommandOptionInput("int", "13")
-                }),
-                new TestCommand {IntOption = 13}
-            );
-
-            yield return new TestCaseData(
-                new TestCommand(),
-                GetCommandSchema(typeof(TestCommand)),
-                new CommandInput(new[]
-                {
-                    new CommandOptionInput("int", "13"),
-                    new CommandOptionInput("str", "hello world")
-                }),
-                new TestCommand {IntOption = 13, StringOption = "hello world"}
-            );
-
-            yield return new TestCaseData(
-                new TestCommand(),
-                GetCommandSchema(typeof(TestCommand)),
-                new CommandInput(new[]
-                {
-                    new CommandOptionInput("i", "13")
-                }),
-                new TestCommand {IntOption = 13}
-            );
-        }
-
-        private static IEnumerable<TestCaseData> GetTestCases_InitializeCommand_Negative()
-        {
-            yield return new TestCaseData(
-                new TestCommand(),
-                GetCommandSchema(typeof(TestCommand)),
-                CommandInput.Empty
-            );
-
-            yield return new TestCaseData(
-                new TestCommand(),
-                GetCommandSchema(typeof(TestCommand)),
-                new CommandInput(new[]
-                {
-                    new CommandOptionInput("str", "hello world")
-                })
-            );
-        }
-
-        [Test]
-        [TestCaseSource(nameof(GetTestCases_InitializeCommand))]
-        public void InitializeCommand_Test(ICommand command, CommandSchema commandSchema, CommandInput commandInput, ICommand expectedCommand)
-        {
-            // Arrange
-            var initializer = new CommandInitializer();
-
-            // Act
-            initializer.InitializeCommand(command, commandSchema, commandInput);
-
-            // Assert
-            command.Should().BeEquivalentTo(expectedCommand, o => o.RespectingRuntimeTypes());
-        }
-
-        [Test]
-        [TestCaseSource(nameof(GetTestCases_InitializeCommand_Negative))]
-        public void InitializeCommand_Negative_Test(ICommand command, CommandSchema commandSchema, CommandInput commandInput)
-        {
-            // Arrange
-            var initializer = new CommandInitializer();
-
-            // Act & Assert
-            initializer.Invoking(i => i.InitializeCommand(command, commandSchema, commandInput))
-                .Should().ThrowExactly<MissingCommandOptionInputException>();
-        }
-    }
-}

CliFx.Tests/CommandOptionInputConverterTests.Types.cs

@@ -1,63 +0,0 @@
-using System;
-
-namespace CliFx.Tests
-{
-    public partial class CommandOptionInputConverterTests
-    {
-        private enum TestEnum
-        {
-            Value1,
-            Value2,
-            Value3
-        }
-
-        private class TestStringConstructable
-        {
-            public string Value { get; }
-
-            public TestStringConstructable(string value)
-            {
-                Value = value;
-            }
-        }
-
-        private class TestStringParseable
-        {
-            public string Value { get; }
-
-            private TestStringParseable(string value)
-            {
-                Value = value;
-            }
-
-            public static TestStringParseable Parse(string value) => new TestStringParseable(value);
-        }
-
-        private class TestStringParseableWithFormatProvider
-        {
-            public string Value { get; }
-
-            private TestStringParseableWithFormatProvider(string value)
-            {
-                Value = value;
-            }
-
-            public static TestStringParseableWithFormatProvider Parse(string value, IFormatProvider formatProvider) =>
-                new TestStringParseableWithFormatProvider(value + " " + formatProvider);
-        }
-    }
-
-    // Negative
-    public partial class CommandOptionInputConverterTests
-    {
-        private class NonStringParseable
-        {
-            public int Value { get; }
-
-            public NonStringParseable(int value)
-            {
-                Value = value;
-            }
-        }
-    }
-}

CliFx.Tests/CommandSchemaResolverTests.Commands.cs

@@ -1,81 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class CommandSchemaResolverTests
-    {
-        [Command("cmd", Description = "NormalCommand1 description.")]
-        private class NormalCommand1 : ICommand
-        {
-            [CommandOption("option-a", 'a')]
-            public int OptionA { get; set; }
-
-            [CommandOption("option-b", IsRequired = true)]
-            public string OptionB { get; set; }
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command(Description = "NormalCommand2 description.")]
-        private class NormalCommand2 : ICommand
-        {
-            [CommandOption("option-c", Description = "OptionC description.")]
-            public bool OptionC { get; set; }
-
-            [CommandOption("option-d", 'd')]
-            public DateTimeOffset OptionD { get; set; }
-
-            public string NotAnOption { get; set; }
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-
-    // Negative
-    public partial class CommandSchemaResolverTests
-    {
-        [Command("conflict")]
-        private class ConflictingCommand1 : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command("conflict")]
-        private class ConflictingCommand2 : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command]
-        private class InvalidCommand1
-        {
-        }
-
-        [Command]
-        private class InvalidCommand2 : ICommand
-        {
-            [CommandOption("conflict")]
-            public string ConflictingOption1 { get; set; }
-
-            [CommandOption("conflict")]
-            public string ConflictingOption2 { get; set; }
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command]
-        private class InvalidCommand3 : ICommand
-        {
-            [CommandOption('c')]
-            public string ConflictingOption1 { get; set; }
-
-            [CommandOption('c')]
-            public string ConflictingOption2 { get; set; }
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests/CommandSchemaResolverTests.cs

@@ -1,94 +0,0 @@
-using System;
-using System.Collections.Generic;
-using CliFx.Exceptions;
-using CliFx.Models;
-using CliFx.Services;
-using FluentAssertions;
-using NUnit.Framework;
-
-namespace CliFx.Tests
-{
-    [TestFixture]
-    public partial class CommandSchemaResolverTests
-    {
-        private static IEnumerable<TestCaseData> GetTestCases_GetCommandSchemas()
-        {
-            yield return new TestCaseData(
-                new[] {typeof(NormalCommand1), typeof(NormalCommand2)},
-                new[]
-                {
-                    new CommandSchema(typeof(NormalCommand1), "cmd", "NormalCommand1 description.",
-                        new[]
-                        {
-                            new CommandOptionSchema(typeof(NormalCommand1).GetProperty(nameof(NormalCommand1.OptionA)),
-                                "option-a", 'a', false, null),
-                            new CommandOptionSchema(typeof(NormalCommand1).GetProperty(nameof(NormalCommand1.OptionB)),
-                                "option-b", null, true, null)
-                        }),
-                    new CommandSchema(typeof(NormalCommand2), null, "NormalCommand2 description.",
-                        new[]
-                        {
-                            new CommandOptionSchema(typeof(NormalCommand2).GetProperty(nameof(NormalCommand2.OptionC)),
-                                "option-c", null, false, "OptionC description."),
-                            new CommandOptionSchema(typeof(NormalCommand2).GetProperty(nameof(NormalCommand2.OptionD)),
-                                "option-d", 'd', false, null)
-                        })
-                }
-            );
-        }
-
-        private static IEnumerable<TestCaseData> GetTestCases_GetCommandSchemas_Negative()
-        {
-            yield return new TestCaseData(new object[]
-            {
-                new Type[0]
-            });
-
-            yield return new TestCaseData(new object[]
-            {
-                new[] {typeof(ConflictingCommand1), typeof(ConflictingCommand2)}
-            });
-
-            yield return new TestCaseData(new object[]
-            {
-                new[] {typeof(InvalidCommand1)}
-            });
-
-            yield return new TestCaseData(new object[]
-            {
-                new[] {typeof(InvalidCommand2)}
-            });
-
-            yield return new TestCaseData(new object[]
-            {
-                new[] {typeof(InvalidCommand3)}
-            });
-        }
-
-        [Test]
-        [TestCaseSource(nameof(GetTestCases_GetCommandSchemas))]
-        public void GetCommandSchemas_Test(IReadOnlyList<Type> commandTypes, IReadOnlyList<CommandSchema> expectedCommandSchemas)
-        {
-            // Arrange
-            var commandSchemaResolver = new CommandSchemaResolver();
-
-            // Act
-            var commandSchemas = commandSchemaResolver.GetCommandSchemas(commandTypes);
-
-            // Assert
-            commandSchemas.Should().BeEquivalentTo(expectedCommandSchemas);
-        }
-
-        [Test]
-        [TestCaseSource(nameof(GetTestCases_GetCommandSchemas_Negative))]
-        public void GetCommandSchemas_Negative_Test(IReadOnlyList<Type> commandTypes)
-        {
-            // Arrange
-            var resolver = new CommandSchemaResolver();
-
-            // Act & Assert
-            resolver.Invoking(r => r.GetCommandSchemas(commandTypes))
-                .Should().ThrowExactly<InvalidCommandSchemaException>();
-        }
-    }
-}

CliFx.Tests/DelegateCommandFactoryTests.Commands.cs

@@ -1,15 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class DelegateCommandFactoryTests
-    {
-        [Command]
-        private class TestCommand : ICommand
-        {
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests/DummyTests.cs

@@ -1,73 +0,0 @@
-using System.Threading.Tasks;
-using CliWrap;
-using FluentAssertions;
-using NUnit.Framework;
-
-namespace CliFx.Tests
-{
-    [TestFixture]
-    public class DummyTests
-    {
-        private static string DummyFilePath => typeof(Dummy.Program).Assembly.Location;
-
-        private static string DummyVersionText => typeof(Dummy.Program).Assembly.GetName().Version.ToString();
-
-        [Test]
-        [TestCase("", "Hello world")]
-        [TestCase("-t .NET", "Hello .NET")]
-        [TestCase("-e", "Hello world!")]
-        [TestCase("sum -v 1 2", "3")]
-        [TestCase("sum -v 2.75 3.6 4.18", "10.53")]
-        [TestCase("sum -v 4 -v 16", "20")]
-        [TestCase("sum --values 2 5 --values 3", "10")]
-        [TestCase("log -v 100", "2")]
-        [TestCase("log --value 256 --base 2", "8")]
-        public async Task CliApplication_RunAsync_Test(string arguments, string expectedOutput)
-        {
-            // Arrange & Act
-            var result = await Cli.Wrap(DummyFilePath)
-                .SetArguments(arguments)
-                .EnableExitCodeValidation()
-                .EnableStandardErrorValidation()
-                .ExecuteAsync();
-
-            // Assert
-            result.StandardOutput.Trim().Should().Be(expectedOutput);
-        }
-
-        [Test]
-        [TestCase("--version")]
-        public async Task CliApplication_RunAsync_ShowVersion_Test(string arguments)
-        {
-            // Arrange & Act
-            var result = await Cli.Wrap(DummyFilePath)
-                .SetArguments(arguments)
-                .EnableExitCodeValidation()
-                .EnableStandardErrorValidation()
-                .ExecuteAsync();
-
-            // Assert
-            result.StandardOutput.Trim().Should().Be(DummyVersionText);
-        }
-
-        [Test]
-        [TestCase("--help")]
-        [TestCase("-h")]
-        [TestCase("sum -h")]
-        [TestCase("sum --help")]
-        [TestCase("log -h")]
-        [TestCase("log --help")]
-        public async Task CliApplication_RunAsync_ShowHelp_Test(string arguments)
-        {
-            // Arrange & Act
-            var result = await Cli.Wrap(DummyFilePath)
-                .SetArguments(arguments)
-                .EnableExitCodeValidation()
-                .EnableStandardErrorValidation()
-                .ExecuteAsync();
-
-            // Assert
-            result.StandardOutput.Trim().Should().NotBeNullOrWhiteSpace();
-        }
-    }
-}

CliFx.Tests/HelpTextRendererTests.Commands.cs

@@ -1,42 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Services;
-
-namespace CliFx.Tests
-{
-    public partial class HelpTextRendererTests
-    {
-        [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 Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command("cmd", Description = "NamedCommand description.")]
-        private class NamedCommand : ICommand
-        {
-            [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 Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-
-        [Command("cmd sub", Description = "NamedSubCommand description.")]
-        private class NamedSubCommand : ICommand
-        {
-            [CommandOption("option-e", 'e', Description = "OptionE description.")]
-            public string OptionE { get; set; }
-
-            public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
-        }
-    }
-}

CliFx.Tests/Services/CommandFactoryTests.cs

@@ -3,20 +3,21 @@ using System.Collections.Generic;
 using System.Linq;
 using CliFx.Models;
 using CliFx.Services;
+using CliFx.Tests.TestCommands;
 using FluentAssertions;
 using NUnit.Framework;
 
-namespace CliFx.Tests
+namespace CliFx.Tests.Services
 {
     [TestFixture]
-    public partial class CommandFactoryTests
+    public class CommandFactoryTests
     {
         private static CommandSchema GetCommandSchema(Type commandType) =>
             new CommandSchemaResolver().GetCommandSchemas(new[] {commandType}).Single();
 
         private static IEnumerable<TestCaseData> GetTestCases_CreateCommand()
         {
-            yield return new TestCaseData(GetCommandSchema(typeof(TestCommand)));
+            yield return new TestCaseData(GetCommandSchema(typeof(HelloWorldDefaultCommand)));
         }
 
         [Test]

CliFx.Tests/Services/CommandInitializerTests.cs

@@ -0,0 +1,136 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using CliFx.Exceptions;
+using CliFx.Models;
+using CliFx.Services;
+using CliFx.Tests.TestCommands;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests.Services
+{
+    [TestFixture]
+    public class CommandInitializerTests
+    {
+        private static CommandSchema GetCommandSchema(Type commandType) =>
+            new CommandSchemaResolver().GetCommandSchemas(new[] {commandType}).Single();
+
+        private static IEnumerable<TestCaseData> GetTestCases_InitializeCommand()
+        {
+            yield return new TestCaseData(
+                new DivideCommand(),
+                GetCommandSchema(typeof(DivideCommand)),
+                new CommandInput("div", new[]
+                {
+                    new CommandOptionInput("dividend", "13"),
+                    new CommandOptionInput("divisor", "8")
+                }),
+                new DivideCommand {Dividend = 13, Divisor = 8}
+            );
+
+            yield return new TestCaseData(
+                new DivideCommand(),
+                GetCommandSchema(typeof(DivideCommand)),
+                new CommandInput("div", new[]
+                {
+                    new CommandOptionInput("dividend", "13"),
+                    new CommandOptionInput("d", "8")
+                }),
+                new DivideCommand {Dividend = 13, Divisor = 8}
+            );
+
+            yield return new TestCaseData(
+                new DivideCommand(),
+                GetCommandSchema(typeof(DivideCommand)),
+                new CommandInput("div", new[]
+                {
+                    new CommandOptionInput("D", "13"),
+                    new CommandOptionInput("d", "8")
+                }),
+                new DivideCommand {Dividend = 13, Divisor = 8}
+            );
+
+            yield return new TestCaseData(
+                new ConcatCommand(),
+                GetCommandSchema(typeof(ConcatCommand)),
+                new CommandInput("concat", new[]
+                {
+                    new CommandOptionInput("i", new[] {"foo", " ", "bar"})
+                }),
+                new ConcatCommand {Inputs = new[] {"foo", " ", "bar"}}
+            );
+
+            yield return new TestCaseData(
+                new ConcatCommand(),
+                GetCommandSchema(typeof(ConcatCommand)),
+                new CommandInput("concat", new[]
+                {
+                    new CommandOptionInput("i", new[] {"foo", "bar"}),
+                    new CommandOptionInput("s", " ")
+                }),
+                new ConcatCommand {Inputs = new[] {"foo", "bar"}, Separator = " "}
+            );
+        }
+
+        private static IEnumerable<TestCaseData> GetTestCases_InitializeCommand_Negative()
+        {
+            yield return new TestCaseData(
+                new DivideCommand(),
+                GetCommandSchema(typeof(DivideCommand)),
+                new CommandInput("div")
+            );
+
+            yield return new TestCaseData(
+                new DivideCommand(),
+                GetCommandSchema(typeof(DivideCommand)),
+                new CommandInput("div", new[]
+                {
+                    new CommandOptionInput("D", "13")
+                })
+            );
+
+            yield return new TestCaseData(
+                new ConcatCommand(),
+                GetCommandSchema(typeof(ConcatCommand)),
+                new CommandInput("concat")
+            );
+
+            yield return new TestCaseData(
+                new ConcatCommand(),
+                GetCommandSchema(typeof(ConcatCommand)),
+                new CommandInput("concat", new[]
+                {
+                    new CommandOptionInput("s", "_")
+                })
+            );
+        }
+
+        [Test]
+        [TestCaseSource(nameof(GetTestCases_InitializeCommand))]
+        public void InitializeCommand_Test(ICommand command, CommandSchema commandSchema, CommandInput commandInput,
+            ICommand expectedCommand)
+        {
+            // Arrange
+            var initializer = new CommandInitializer();
+
+            // Act
+            initializer.InitializeCommand(command, commandSchema, commandInput);
+
+            // Assert
+            command.Should().BeEquivalentTo(expectedCommand, o => o.RespectingRuntimeTypes());
+        }
+
+        [Test]
+        [TestCaseSource(nameof(GetTestCases_InitializeCommand_Negative))]
+        public void InitializeCommand_Negative_Test(ICommand command, CommandSchema commandSchema, CommandInput commandInput)
+        {
+            // Arrange
+            var initializer = new CommandInitializer();
+
+            // Act & Assert
+            initializer.Invoking(i => i.InitializeCommand(command, commandSchema, commandInput))
+                .Should().ThrowExactly<CliFxException>();
+        }
+    }
+}

CliFx.Tests/Services/CommandInputParserTests.cs

@@ -4,7 +4,7 @@ using CliFx.Services;
 using FluentAssertions;
 using NUnit.Framework;
 
-namespace CliFx.Tests
+namespace CliFx.Tests.Services
 {
     [TestFixture]
     public class CommandInputParserTests
@@ -165,11 +165,46 @@ namespace CliFx.Tests
                     new CommandOptionInput("option", "value")
                 })
             );
+
+            yield return new TestCaseData(
+                new[] {"[debug]"},
+                new CommandInput(null,
+                    new[] {"debug"},
+                    new CommandOptionInput[0])
+            );
+
+            yield return new TestCaseData(
+                new[] {"[debug]", "[preview]"},
+                new CommandInput(null,
+                    new[] {"debug", "preview"},
+                    new CommandOptionInput[0])
+            );
+
+            yield return new TestCaseData(
+                new[] {"[debug]", "[preview]", "-o", "value"},
+                new CommandInput(null,
+                    new[] {"debug", "preview"},
+                    new[]
+                    {
+                        new CommandOptionInput("o", "value")
+                    })
+            );
+
+            yield return new TestCaseData(
+                new[] {"command", "[debug]", "[preview]", "-o", "value"},
+                new CommandInput("command",
+                    new[] {"debug", "preview"},
+                    new[]
+                    {
+                        new CommandOptionInput("o", "value")
+                    })
+            );
         }
 
         [Test]
         [TestCaseSource(nameof(GetTestCases_ParseCommandInput))]
-        public void ParseCommandInput_Test(IReadOnlyList<string> commandLineArguments, CommandInput expectedCommandInput)
+        public void ParseCommandInput_Test(IReadOnlyList<string> commandLineArguments,
+            CommandInput expectedCommandInput)
         {
             // Arrange
             var parser = new CommandInputParser();

CliFx.Tests/Services/CommandOptionInputConverterTests.cs

@@ -5,13 +5,14 @@ using System.Globalization;
 using CliFx.Exceptions;
 using CliFx.Models;
 using CliFx.Services;
+using CliFx.Tests.TestCustomTypes;
 using FluentAssertions;
 using NUnit.Framework;
 
-namespace CliFx.Tests
+namespace CliFx.Tests.Services
 {
     [TestFixture]
-    public partial class CommandOptionInputConverterTests
+    public class CommandOptionInputConverterTests
     {
         private static IEnumerable<TestCaseData> GetTestCases_ConvertOptionInput()
         {
@@ -271,13 +272,14 @@ namespace CliFx.Tests
 
             yield return new TestCaseData(
                 new CommandOptionInput("option", "123"),
-                typeof(NonStringParseable)
+                typeof(TestNonStringParseable)
             );
         }
 
         [Test]
         [TestCaseSource(nameof(GetTestCases_ConvertOptionInput))]
-        public void ConvertOptionInput_Test(CommandOptionInput optionInput, Type targetType, object expectedConvertedValue)
+        public void ConvertOptionInput_Test(CommandOptionInput optionInput, Type targetType,
+            object expectedConvertedValue)
         {
             // Arrange
             var converter = new CommandOptionInputConverter();
@@ -299,7 +301,7 @@ namespace CliFx.Tests
 
             // Act & Assert
             converter.Invoking(c => c.ConvertOptionInput(optionInput, targetType))
-                .Should().ThrowExactly<InvalidCommandOptionInputException>();
+                .Should().ThrowExactly<CliFxException>();
         }
     }
 }

CliFx.Tests/Services/CommandSchemaResolverTests.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Collections.Generic;
+using CliFx.Exceptions;
+using CliFx.Models;
+using CliFx.Services;
+using CliFx.Tests.TestCommands;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests.Services
+{
+    [TestFixture]
+    public class CommandSchemaResolverTests
+    {
+        private static IEnumerable<TestCaseData> GetTestCases_GetCommandSchemas()
+        {
+            yield return new TestCaseData(
+                new[] {typeof(DivideCommand), typeof(ConcatCommand)},
+                new[]
+                {
+                    new CommandSchema(typeof(DivideCommand), "div", "Divide one number by another.",
+                        new[]
+                        {
+                            new CommandOptionSchema(typeof(DivideCommand).GetProperty(nameof(DivideCommand.Dividend)),
+                                "dividend", 'D', true, "The number to divide."),
+                            new CommandOptionSchema(typeof(DivideCommand).GetProperty(nameof(DivideCommand.Divisor)),
+                                "divisor", 'd', true, "The number to divide by.")
+                        }),
+                    new CommandSchema(typeof(ConcatCommand), "concat", "Concatenate strings.",
+                        new[]
+                        {
+                            new CommandOptionSchema(typeof(ConcatCommand).GetProperty(nameof(ConcatCommand.Inputs)),
+                                null, 'i', true, "Input strings."),
+                            new CommandOptionSchema(typeof(ConcatCommand).GetProperty(nameof(ConcatCommand.Separator)),
+                                null, 's', false, "String separator.")
+                        })
+                }
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(HelloWorldDefaultCommand)},
+                new[]
+                {
+                    new CommandSchema(typeof(HelloWorldDefaultCommand), null, null, new CommandOptionSchema[0])
+                }
+            );
+        }
+
+        private static IEnumerable<TestCaseData> GetTestCases_GetCommandSchemas_Negative()
+        {
+            yield return new TestCaseData(new object[]
+            {
+                new Type[0]
+            });
+
+            yield return new TestCaseData(new object[]
+            {
+                new[] {typeof(NonImplementedCommand)}
+            });
+
+            yield return new TestCaseData(new object[]
+            {
+                new[] {typeof(NonAnnotatedCommand)}
+            });
+            
+            yield return new TestCaseData(new object[]
+            {
+                new[] {typeof(DuplicateOptionNamesCommand)}
+            });
+
+            yield return new TestCaseData(new object[]
+            {
+                new[] {typeof(DuplicateOptionShortNamesCommand)}
+            });
+            
+            yield return new TestCaseData(new object[]
+            {
+                new[] {typeof(ExceptionCommand), typeof(CommandExceptionCommand)}
+            });
+        }
+
+        [Test]
+        [TestCaseSource(nameof(GetTestCases_GetCommandSchemas))]
+        public void GetCommandSchemas_Test(IReadOnlyList<Type> commandTypes,
+            IReadOnlyList<CommandSchema> expectedCommandSchemas)
+        {
+            // Arrange
+            var commandSchemaResolver = new CommandSchemaResolver();
+
+            // Act
+            var commandSchemas = commandSchemaResolver.GetCommandSchemas(commandTypes);
+
+            // Assert
+            commandSchemas.Should().BeEquivalentTo(expectedCommandSchemas);
+        }
+
+        [Test]
+        [TestCaseSource(nameof(GetTestCases_GetCommandSchemas_Negative))]
+        public void GetCommandSchemas_Negative_Test(IReadOnlyList<Type> commandTypes)
+        {
+            // Arrange
+            var resolver = new CommandSchemaResolver();
+
+            // Act & Assert
+            resolver.Invoking(r => r.GetCommandSchemas(commandTypes))
+                .Should().ThrowExactly<CliFxException>();
+        }
+    }
+}

CliFx.Tests/Services/DelegateCommandFactoryTests.cs

@@ -3,13 +3,14 @@ using System.Collections.Generic;
 using System.Linq;
 using CliFx.Models;
 using CliFx.Services;
+using CliFx.Tests.TestCommands;
 using FluentAssertions;
 using NUnit.Framework;
 
-namespace CliFx.Tests
+namespace CliFx.Tests.Services
 {
     [TestFixture]
-    public partial class DelegateCommandFactoryTests
+    public class DelegateCommandFactoryTests
     {
         private static CommandSchema GetCommandSchema(Type commandType) =>
             new CommandSchemaResolver().GetCommandSchemas(new[] {commandType}).Single();
@@ -18,7 +19,7 @@ namespace CliFx.Tests
         {
             yield return new TestCaseData(
                 new Func<CommandSchema, ICommand>(schema => (ICommand) Activator.CreateInstance(schema.Type)),
-                GetCommandSchema(typeof(TestCommand))
+                GetCommandSchema(typeof(HelloWorldDefaultCommand))
             );
         }
 

CliFx.Tests/Services/HelpTextRendererTests.cs

@@ -4,13 +4,14 @@ using System.IO;
 using System.Linq;
 using CliFx.Models;
 using CliFx.Services;
+using CliFx.Tests.TestCommands;
 using FluentAssertions;
 using NUnit.Framework;
 
-namespace CliFx.Tests
+namespace CliFx.Tests.Services
 {
     [TestFixture]
-    public partial class HelpTextRendererTests
+    public class HelpTextRendererTests
     {
         private static HelpTextSource CreateHelpTextSource(IReadOnlyList<Type> availableCommandTypes, Type targetCommandType)
         {
@@ -27,11 +28,13 @@ namespace CliFx.Tests
         {
             yield return new TestCaseData(
                 CreateHelpTextSource(
-                    new[] {typeof(DefaultCommand), typeof(NamedCommand), typeof(NamedSubCommand)},
-                    typeof(DefaultCommand)),
+                    new[] {typeof(HelpDefaultCommand), typeof(HelpNamedCommand), typeof(HelpSubCommand)},
+                    typeof(HelpDefaultCommand)),
 
                 new[]
                 {
+                    "Description",
+                    "HelpDefaultCommand description.",
                     "Usage",
                     "[command]", "[options]",
                     "Options",
@@ -40,20 +43,20 @@ namespace CliFx.Tests
                     "-h|--help", "Shows help text.",
                     "--version", "Shows version information.",
                     "Commands",
-                    "cmd", "NamedCommand description.",
+                    "cmd", "HelpNamedCommand description.",
                     "You can run", "to show help on a specific command."
                 }
             );
 
             yield return new TestCaseData(
                 CreateHelpTextSource(
-                    new[] {typeof(DefaultCommand), typeof(NamedCommand), typeof(NamedSubCommand)},
-                    typeof(NamedCommand)),
+                    new[] {typeof(HelpDefaultCommand), typeof(HelpNamedCommand), typeof(HelpSubCommand)},
+                    typeof(HelpNamedCommand)),
 
                 new[]
                 {
                     "Description",
-                    "NamedCommand description.",
+                    "HelpNamedCommand description.",
                     "Usage",
                     "cmd", "[command]", "[options]",
                     "Options",
@@ -61,20 +64,20 @@ namespace CliFx.Tests
                     "-d|--option-d", "OptionD description.",
                     "-h|--help", "Shows help text.",
                     "Commands",
-                    "sub", "NamedSubCommand description.",
+                    "sub", "HelpSubCommand description.",
                     "You can run", "to show help on a specific command."
                 }
             );
 
             yield return new TestCaseData(
                 CreateHelpTextSource(
-                    new[] {typeof(DefaultCommand), typeof(NamedCommand), typeof(NamedSubCommand)},
-                    typeof(NamedSubCommand)),
+                    new[] {typeof(HelpDefaultCommand), typeof(HelpNamedCommand), typeof(HelpSubCommand)},
+                    typeof(HelpSubCommand)),
 
                 new[]
                 {
                     "Description",
-                    "NamedSubCommand description.",
+                    "HelpSubCommand description.",
                     "Usage",
                     "cmd sub", "[options]",
                     "Options",
@@ -86,13 +89,14 @@ namespace CliFx.Tests
 
         [Test]
         [TestCaseSource(nameof(GetTestCases_RenderHelpText))]
-        public void RenderHelpText_Test(HelpTextSource source, IReadOnlyList<string> expectedSubstrings)
+        public void RenderHelpText_Test(HelpTextSource source,
+            IReadOnlyList<string> expectedSubstrings)
         {
             // Arrange
             using (var stdout = new StringWriter())
             {
-                var renderer = new HelpTextRenderer();
                 var console = new VirtualConsole(stdout);
+                var renderer = new HelpTextRenderer();
 
                 // Act
                 renderer.RenderHelpText(console, source);

CliFx.Tests/Services/SystemConsoleTests.cs

@@ -0,0 +1,41 @@
+using System;
+using CliFx.Services;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests.Services
+{
+    [TestFixture]
+    public class SystemConsoleTests
+    {
+        [TearDown]
+        public void TearDown()
+        {
+            // Reset console color so it doesn't carry on into next tests
+            Console.ResetColor();
+        }
+        
+        // Make sure console correctly wraps around System.Console
+        [Test]
+        public void All_Smoke_Test()
+        {
+            // Arrange
+            var console = new SystemConsole();
+
+            // Act
+            console.ResetColor();
+            console.ForegroundColor = ConsoleColor.DarkMagenta;
+            console.BackgroundColor = ConsoleColor.DarkMagenta;
+
+            // Assert
+            console.Input.Should().BeSameAs(Console.In);
+            console.IsInputRedirected.Should().Be(Console.IsInputRedirected);
+            console.Output.Should().BeSameAs(Console.Out);
+            console.IsOutputRedirected.Should().Be(Console.IsOutputRedirected);
+            console.Error.Should().BeSameAs(Console.Error);
+            console.IsErrorRedirected.Should().Be(Console.IsErrorRedirected);
+            console.ForegroundColor.Should().Be(Console.ForegroundColor);
+            console.BackgroundColor.Should().Be(Console.BackgroundColor);
+        }
+    }
+}

CliFx.Tests/Services/VirtualConsoleTests.cs

@@ -0,0 +1,43 @@
+using System;
+using System.IO;
+using CliFx.Services;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests.Services
+{
+    [TestFixture]
+    public class VirtualConsoleTests
+    {
+        // Make sure console uses specified streams and doesn't leak to System.Console
+        [Test]
+        public void All_Smoke_Test()
+        {
+            // Arrange
+            using (var stdin = new StringReader("hello world"))
+            using (var stdout = new StringWriter())
+            using (var stderr = new StringWriter())
+            {
+                var console = new VirtualConsole(stdin, stdout, stderr);
+
+                // Act
+                console.ResetColor();
+                console.ForegroundColor = ConsoleColor.DarkMagenta;
+                console.BackgroundColor = ConsoleColor.DarkMagenta;
+
+                // Assert
+                console.Input.Should().BeSameAs(stdin);
+                console.Input.Should().NotBeSameAs(Console.In);
+                console.IsInputRedirected.Should().BeTrue();
+                console.Output.Should().BeSameAs(stdout);
+                console.Output.Should().NotBeSameAs(Console.Out);
+                console.IsOutputRedirected.Should().BeTrue();
+                console.Error.Should().BeSameAs(stderr);
+                console.Error.Should().NotBeSameAs(Console.Error);
+                console.IsErrorRedirected.Should().BeTrue();
+                console.ForegroundColor.Should().NotBe(Console.ForegroundColor);
+                console.BackgroundColor.Should().NotBe(Console.BackgroundColor);
+            }
+        }
+    }
+}

CliFx.Tests/TestCommands/CommandExceptionCommand.cs

@@ -0,0 +1,19 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Exceptions;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("exc")]
+    public class CommandExceptionCommand : ICommand
+    {
+        [CommandOption("code", 'c')]
+        public int ExitCode { get; set; } = 1337;
+        
+        [CommandOption("msg", 'm')]
+        public string Message { get; set; }
+        
+        public Task ExecuteAsync(IConsole console) => throw new CommandException(Message, ExitCode);
+    }
+}

CliFx.Tests/TestCommands/ConcatCommand.cs

@@ -0,0 +1,23 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("concat", Description = "Concatenate strings.")]
+    public class ConcatCommand : ICommand
+    {
+        [CommandOption('i', IsRequired = true, Description = "Input strings.")]
+        public IReadOnlyList<string> Inputs { get; set; }
+
+        [CommandOption('s', Description = "String separator.")]
+        public string Separator { get; set; } = ""; 
+        
+        public Task ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(string.Join(Separator, Inputs));
+            return Task.CompletedTask;
+        }
+    }
+}

CliFx.Tests/TestCommands/DivideCommand.cs

@@ -0,0 +1,25 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("div", Description = "Divide one number by another.")]
+    public class DivideCommand : ICommand
+    {
+        [CommandOption("dividend", 'D', IsRequired = true, Description = "The number to divide.")]
+        public double Dividend { get; set; }
+
+        [CommandOption("divisor", 'd', IsRequired = true, Description = "The number to divide by.")]
+        public double Divisor { get; set; }
+
+        // This property should be ignored by resolver
+        public bool NotAnOption { get; set; }
+        
+        public Task ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine(Dividend / Divisor);
+            return Task.CompletedTask;
+        }
+    }
+}

CliFx.Tests/TestCommands/DuplicateOptionNamesCommand.cs

@@ -0,0 +1,18 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command]
+    public class DuplicateOptionNamesCommand : ICommand
+    {
+        [CommandOption("fruits")]
+        public string Apples { get; set; }
+        
+        [CommandOption("fruits")]
+        public string Oranges { get; set; }
+        
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/DuplicateOptionShortNamesCommand.cs

@@ -0,0 +1,18 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command]
+    public class DuplicateOptionShortNamesCommand : ICommand
+    {
+        [CommandOption('f')]
+        public string Apples { get; set; }
+        
+        [CommandOption('f')]
+        public string Oranges { get; set; }
+        
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/ExceptionCommand.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("exc")]
+    public class ExceptionCommand : ICommand
+    {
+        [CommandOption("msg", 'm')]
+        public string Message { get; set; }
+        
+        public Task ExecuteAsync(IConsole console) => throw new Exception(Message);
+    }
+}

CliFx.Tests/TestCommands/HelloWorldDefaultCommand.cs

@@ -0,0 +1,16 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command]
+    public class HelloWorldDefaultCommand : ICommand
+    {
+        public Task ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine("Hello world.");
+            return Task.CompletedTask;
+        }
+    }
+}

CliFx.Tests/TestCommands/HelpDefaultCommand.cs

@@ -0,0 +1,18 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command(Description = "HelpDefaultCommand description.")]
+    public class HelpDefaultCommand : 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 Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/HelpNamedCommand.cs

@@ -0,0 +1,18 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("cmd", Description = "HelpNamedCommand description.")]
+    public class HelpNamedCommand : ICommand
+    {
+        [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 Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/HelpSubCommand.cs

@@ -0,0 +1,15 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    [Command("cmd sub", Description = "HelpSubCommand description.")]
+    public class HelpSubCommand : ICommand
+    {
+        [CommandOption("option-e", 'e', Description = "OptionE description.")]
+        public string OptionE { get; set; }
+
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/NonAnnotatedCommand.cs

@@ -0,0 +1,10 @@
+using System.Threading.Tasks;
+using CliFx.Services;
+
+namespace CliFx.Tests.TestCommands
+{
+    public class NonAnnotatedCommand : ICommand
+    {
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
+    }
+}

CliFx.Tests/TestCommands/NonImplementedCommand.cs

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

CliFx.Tests/TestCustomTypes/TestEnum.cs

@@ -0,0 +1,9 @@
+namespace CliFx.Tests.TestCustomTypes
+{
+    public enum TestEnum
+    {
+        Value1,
+        Value2,
+        Value3
+    }
+}

CliFx.Tests/TestCustomTypes/TestNonStringParseable.cs

@@ -0,0 +1,12 @@
+namespace CliFx.Tests.TestCustomTypes
+{
+    public class TestNonStringParseable
+    {
+        public int Value { get; }
+
+        public TestNonStringParseable(int value)
+        {
+            Value = value;
+        }
+    }
+}

CliFx.Tests/TestCustomTypes/TestStringConstructable.cs

@@ -0,0 +1,12 @@
+namespace CliFx.Tests.TestCustomTypes
+{
+    public class TestStringConstructable
+    {
+        public string Value { get; }
+
+        public TestStringConstructable(string value)
+        {
+            Value = value;
+        }
+    }
+}

CliFx.Tests/TestCustomTypes/TestStringParseable.cs

@@ -0,0 +1,14 @@
+namespace CliFx.Tests.TestCustomTypes
+{
+    public class TestStringParseable
+    {
+        public string Value { get; }
+
+        private TestStringParseable(string value)
+        {
+            Value = value;
+        }
+
+        public static TestStringParseable Parse(string value) => new TestStringParseable(value);
+    }
+}

CliFx.Tests/TestCustomTypes/TestStringParseableWithFormatProvider.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace CliFx.Tests.TestCustomTypes
+{
+    public class TestStringParseableWithFormatProvider
+    {
+        public string Value { get; }
+
+        private TestStringParseableWithFormatProvider(string value)
+        {
+            Value = value;
+        }
+
+        public static TestStringParseableWithFormatProvider Parse(string value, IFormatProvider formatProvider) =>
+            new TestStringParseableWithFormatProvider(value + " " + formatProvider);
+    }
+}

CliFx.Tests/Utilities/ProgressTickerTests.cs

@@ -0,0 +1,57 @@
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using CliFx.Services;
+using CliFx.Utilities;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests.Utilities
+{
+    [TestFixture]
+    public class ProgressTickerTests
+    {
+        [Test]
+        public void Report_Test()
+        {
+            // Arrange
+            var formatProvider = CultureInfo.InvariantCulture;
+
+            using (var stdout = new StringWriter(formatProvider))
+            {
+                var console = new VirtualConsole(TextReader.Null, false, stdout, false, TextWriter.Null, false);
+                var ticker = console.CreateProgressTicker();
+
+                var progressValues = Enumerable.Range(0, 100).Select(p => p / 100.0).ToArray();
+                var progressStringValues = progressValues.Select(p => p.ToString("P2", formatProvider)).ToArray();
+
+                // Act
+                foreach (var progress in progressValues)
+                    ticker.Report(progress);
+
+                // Assert
+                stdout.ToString().Should().ContainAll(progressStringValues);
+            }
+        }
+
+        [Test]
+        public void Report_Redirected_Test()
+        {
+            // Arrange
+            using (var stdout = new StringWriter())
+            {
+                var console = new VirtualConsole(stdout);
+                var ticker = console.CreateProgressTicker();
+
+                var progressValues = Enumerable.Range(0, 100).Select(p => p / 100.0).ToArray();
+
+                // Act
+                foreach (var progress in progressValues)
+                    ticker.Report(progress);
+
+                // Assert
+                stdout.ToString().Should().BeEmpty();
+            }
+        }
+    }
+}

CliFx.sln

@@ -7,8 +7,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx", "CliFx\CliFx.csproj
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Tests", "CliFx.Tests\CliFx.Tests.csproj", "{268CF863-65A5-49BB-93CF-08972B7756DC}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Tests.Dummy", "CliFx.Tests.Dummy\CliFx.Tests.Dummy.csproj", "{4904B3EB-3286-4F1B-8B74-6FF051C8E787}"
-EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{3AAE8166-BB8E-49DA-844C-3A0EE6BD40A0}"
 	ProjectSection(SolutionItems) = preProject
 		Changelog.md = Changelog.md
@@ -18,7 +16,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Benchmarks", "CliFx.Benchmarks\CliFx.Benchmarks.csproj", "{8ACD6DC2-D768-4850-9223-5B7C83A78513}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CliFx.Demo", "CliFx.Demo\CliFx.Demo.csproj", "{AAB6844C-BF71-448F-A11B-89AEE459AB15}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Demo", "CliFx.Demo\CliFx.Demo.csproj", "{AAB6844C-BF71-448F-A11B-89AEE459AB15}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -54,18 +52,6 @@ Global
 		{268CF863-65A5-49BB-93CF-08972B7756DC}.Release|x64.Build.0 = Release|Any CPU
 		{268CF863-65A5-49BB-93CF-08972B7756DC}.Release|x86.ActiveCfg = Release|Any CPU
 		{268CF863-65A5-49BB-93CF-08972B7756DC}.Release|x86.Build.0 = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|x64.Build.0 = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Debug|x86.Build.0 = Debug|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|Any CPU.Build.0 = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|x64.ActiveCfg = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|x64.Build.0 = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|x86.ActiveCfg = Release|Any CPU
-		{4904B3EB-3286-4F1B-8B74-6FF051C8E787}.Release|x86.Build.0 = Release|Any CPU
 		{8ACD6DC2-D768-4850-9223-5B7C83A78513}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{8ACD6DC2-D768-4850-9223-5B7C83A78513}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8ACD6DC2-D768-4850-9223-5B7C83A78513}.Debug|x64.ActiveCfg = Debug|Any CPU

CliFx/CliApplication.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
 using CliFx.Exceptions;
@@ -42,75 +43,127 @@ namespace CliFx
             _helpTextRenderer = helpTextRenderer.GuardNotNull(nameof(helpTextRenderer));
         }
 
-        /// <inheritdoc />
-        public async Task<int> RunAsync(IReadOnlyList<string> commandLineArguments)
+        private async Task<int?> HandleDebugDirectiveAsync(CommandInput commandInput)
         {
-            commandLineArguments.GuardNotNull(nameof(commandLineArguments));
+            // Debug mode is enabled if it's allowed in the application and it was requested via corresponding directive
+            var isDebugMode = _configuration.IsDebugModeAllowed && commandInput.IsDebugDirectiveSpecified();
 
-            try
+            // If not in debug mode, pass execution to the next handler
+            if (!isDebugMode)
+                return null;
+
+            // Inform user which process they need to attach debugger to
+            _console.WithForegroundColor(ConsoleColor.Green,
+                () => _console.Output.WriteLine($"Attach debugger to PID {Process.GetCurrentProcess().Id} to continue."));
+
+            // Wait until debugger is attached
+            while (!Debugger.IsAttached)
+                await Task.Delay(100);
+
+            // Debug directive never short-circuits
+            return null;
+        }
+
+        private int? HandlePreviewDirective(CommandInput commandInput)
         {
-                // Get schemas for all available command types
-                var availableCommandSchemas = _commandSchemaResolver.GetCommandSchemas(_configuration.CommandTypes);
+            // Preview mode is enabled if it's allowed in the application and it was requested via corresponding directive
+            var isPreviewMode = _configuration.IsPreviewModeAllowed && commandInput.IsPreviewDirectiveSpecified();
 
-                // Parse command input from arguments
-                var commandInput = _commandInputParser.ParseCommandInput(commandLineArguments);
+            // If not in preview mode, pass execution to the next handler
+            if (!isPreviewMode)
+                return null;
 
-                // Find command schema matching the name specified in the input
-                var targetCommandSchema = availableCommandSchemas.FindByName(commandInput.CommandName);
+            // Render command name
+            _console.Output.WriteLine($"Command name: {commandInput.CommandName}");
+            _console.Output.WriteLine();
 
-                // Handle cases where requested command is not defined
-                if (targetCommandSchema == null)
+            // Render directives
+            _console.Output.WriteLine("Directives:");
+            foreach (var directive in commandInput.Directives)
             {
+                _console.Output.Write(" ");
+                _console.Output.WriteLine(directive);
+            }
+
+            // Margin
+            _console.Output.WriteLine();
+
+            // Render options
+            _console.Output.WriteLine("Options:");
+            foreach (var option in commandInput.Options)
+            {
+                _console.Output.Write(" ");
+                _console.Output.WriteLine(option);
+            }
+
+            // Short-circuit with exit code 0
+            return 0;
+        }
+
+        private int? HandleVersionOption(CommandInput commandInput)
+        {
+            // Version should be rendered if it was requested on a default command
+            var shouldRenderVersion = !commandInput.IsCommandSpecified() && commandInput.IsVersionOptionSpecified();
+
+            // If shouldn't render version, pass execution to the next handler
+            if (!shouldRenderVersion)
+                return null;
+
+            // Render version text
+            _console.Output.WriteLine(_metadata.VersionText);
+
+            // Short-circuit with exit code 0
+            return 0;
+        }
+
+        private int? HandleHelpOption(CommandInput commandInput,
+            IReadOnlyList<CommandSchema> availableCommandSchemas, CommandSchema targetCommandSchema)
+        {
+            // Help should be rendered if it was requested, or when executing a command which isn't defined
+            var shouldRenderHelp = commandInput.IsHelpOptionSpecified() || targetCommandSchema == null;
+
+            // If shouldn't render help, pass execution to the next handler
+            if (!shouldRenderHelp)
+                return null;
+
+            // Keep track whether there was an error in the input
             var isError = false;
 
-                    // If specified a command - show error
+            // If target command isn't defined, find its contextual replacement
+            if (targetCommandSchema == null)
+            {
+                // If command was specified, inform the user that it's not defined
                 if (commandInput.IsCommandSpecified())
                 {
-                        isError = true;
-
                     _console.WithForegroundColor(ConsoleColor.Red,
                         () => _console.Error.WriteLine($"Specified command [{commandInput.CommandName}] is not defined."));
+
+                    isError = true;
                 }
 
-                    // Get parent command schema
-                    var parentCommandSchema = availableCommandSchemas.FindParent(commandInput.CommandName);
+                // Replace target command with closest parent of specified command
+                targetCommandSchema = availableCommandSchemas.FindParent(commandInput.CommandName);
 
-                    // Show help for parent command if it's defined
-                    if (parentCommandSchema != null)
+                // If there's no parent, replace with stub default command
+                if (targetCommandSchema == null)
                 {
-                        var helpTextSource = new HelpTextSource(_metadata, availableCommandSchemas, parentCommandSchema);
-                        _helpTextRenderer.RenderHelpText(_console, helpTextSource);
+                    targetCommandSchema = CommandSchema.StubDefaultCommand;
+                    availableCommandSchemas = availableCommandSchemas.Concat(CommandSchema.StubDefaultCommand).ToArray();
                 }
-                    // Otherwise show help for a stub default command
-                    else
-                    {
-                        var helpTextSource = new HelpTextSource(_metadata,
-                            availableCommandSchemas.Concat(CommandSchema.StubDefaultCommand).ToArray(),
-                            CommandSchema.StubDefaultCommand);
-
-                        _helpTextRenderer.RenderHelpText(_console, helpTextSource);
             }
 
+            // Build help text source
+            var helpTextSource = new HelpTextSource(_metadata, availableCommandSchemas, targetCommandSchema);
+
+            // Render help text
+            _helpTextRenderer.RenderHelpText(_console, helpTextSource);
+
+            // Short-circuit with appropriate exit code
             return isError ? -1 : 0;
         }
 
-                // Show version if it was requested without specifying a command
-                if (commandInput.IsVersionRequested() && !commandInput.IsCommandSpecified())
+        private async Task<int> HandleCommandExecutionAsync(CommandInput commandInput, CommandSchema targetCommandSchema)
         {
-                    _console.Output.WriteLine(_metadata.VersionText);
-
-                    return 0;
-                }
-
-                // Show help if it was requested
-                if (commandInput.IsHelpRequested())
-                {
-                    var helpTextSource = new HelpTextSource(_metadata, availableCommandSchemas, targetCommandSchema);
-                    _helpTextRenderer.RenderHelpText(_console, helpTextSource);
-
-                    return 0;
-                }
-
             // Create an instance of the command
             var command = _commandFactory.CreateCommand(targetCommandSchema);
 
@@ -120,24 +173,58 @@ namespace CliFx
             // Execute command
             await command.ExecuteAsync(_console);
 
+            // Finish the chain with exit code 0
             return 0;
         }
+
+        /// <inheritdoc />
+        public async Task<int> RunAsync(IReadOnlyList<string> commandLineArguments)
+        {
+            commandLineArguments.GuardNotNull(nameof(commandLineArguments));
+
+            try
+            {
+                // Parse command input from arguments
+                var commandInput = _commandInputParser.ParseCommandInput(commandLineArguments);
+
+                // Get schemas for all available command types
+                var availableCommandSchemas = _commandSchemaResolver.GetCommandSchemas(_configuration.CommandTypes);
+
+                // Find command schema matching the name specified in the input
+                var targetCommandSchema = availableCommandSchemas.FindByName(commandInput.CommandName);
+
+                // Chain handlers until the first one that produces an exit code
+                return
+                    await HandleDebugDirectiveAsync(commandInput) ??
+                    HandlePreviewDirective(commandInput) ??
+                    HandleVersionOption(commandInput) ??
+                    HandleHelpOption(commandInput, availableCommandSchemas, targetCommandSchema) ??
+                    await HandleCommandExecutionAsync(commandInput, targetCommandSchema);
+            }
             catch (Exception ex)
             {
                 // We want to catch exceptions in order to print errors and return correct exit codes.
-                // Also, by doing this we get rid of the annoying Windows troubleshooting dialog that shows up on unhandled exceptions.
+                // Doing this also gets rid of the annoying Windows troubleshooting dialog that shows up on unhandled exceptions.
 
-                // In case we catch a CliFx-specific exception, we want to just show the error message, not the stack trace.
-                // Stack trace isn't very useful to the user if the exception is not really coming from their code.
+                // Prefer showing message without stack trace on exceptions coming from CliFx or on CommandException
+                if (!ex.Message.IsNullOrWhiteSpace() && (ex is CliFxException || ex is CommandException))
+                {
+                    _console.WithForegroundColor(ConsoleColor.Red, () => _console.Error.WriteLine(ex.Message));
+                }
+                else
+                {
+                    _console.WithForegroundColor(ConsoleColor.Red, () => _console.Error.WriteLine(ex));
+                }
 
-                // CommandException is the same, but it also lets users specify exit code so we want to return that instead of default.
-
-                var message = ex is CliFxException && !ex.Message.IsNullOrWhiteSpace() ? ex.Message : ex.ToString();
-                var exitCode = ex is CommandException commandEx ? commandEx.ExitCode : ex.HResult;
-
-                _console.WithForegroundColor(ConsoleColor.Red, () => _console.Error.WriteLine(message));
-
-                return exitCode;
+                // Return exit code if it was specified via CommandException
+                if (ex is CommandException commandException)
+                {
+                    return commandException.ExitCode;
+                }
+                else
+                {
+                    return ex.HResult;
+                }
             }
         }
     }

CliFx/CliApplicationBuilder.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using CliFx.Attributes;
 using CliFx.Internal;
 using CliFx.Models;
 using CliFx.Services;
@@ -16,6 +17,8 @@ namespace CliFx
     {
         private readonly HashSet<Type> _commandTypes = new HashSet<Type>();
 
+        private bool _isDebugModeAllowed = true;
+        private bool _isPreviewModeAllowed = true;
         private string _title;
         private string _executableName;
         private string _versionText;
@@ -38,7 +41,10 @@ namespace CliFx
         {
             commandAssembly.GuardNotNull(nameof(commandAssembly));
 
-            var commandTypes = commandAssembly.ExportedTypes.Where(t => t.Implements(typeof(ICommand)));
+            var commandTypes = commandAssembly.ExportedTypes
+                .Where(t => t.Implements(typeof(ICommand)))
+                .Where(t => t.IsDefined(typeof(CommandAttribute)))
+                .Where(t => !t.IsAbstract && !t.IsInterface);
 
             foreach (var commandType in commandTypes)
                 AddCommand(commandType);
@@ -46,6 +52,20 @@ namespace CliFx
             return this;
         }
 
+        /// <inheritdoc />
+        public ICliApplicationBuilder AllowDebugMode(bool isAllowed = true)
+        {
+            _isDebugModeAllowed = isAllowed;
+            return this;
+        }
+
+        /// <inheritdoc />
+        public ICliApplicationBuilder AllowPreviewMode(bool isAllowed = true)
+        {
+            _isPreviewModeAllowed = isAllowed;
+            return this;
+        }
+
         /// <inheritdoc />
         public ICliApplicationBuilder UseTitle(string title)
         {
@@ -88,66 +108,19 @@ namespace CliFx
             return this;
         }
 
-        private void SetFallbackValues()
-        {
-            if (_title.IsNullOrWhiteSpace())
-            {
-                // Entry assembly is null in tests
-                UseTitle(EntryAssembly?.GetName().Name ?? "App");
-            }
-
-            if (_executableName.IsNullOrWhiteSpace())
-            {
-                // Entry assembly is null in tests
-                var entryAssemblyLocation = EntryAssembly?.Location;
-
-                // Set different executable name depending on location
-                if (!entryAssemblyLocation.IsNullOrWhiteSpace())
-                {
-                    // Prepend 'dotnet' to assembly file name if the entry assembly is a dll file (extension needs to be kept)
-                    if (string.Equals(Path.GetExtension(entryAssemblyLocation), ".dll", StringComparison.OrdinalIgnoreCase))
-                    {
-                        UseExecutableName("dotnet " + Path.GetFileName(entryAssemblyLocation));
-                    }
-                    // Otherwise just use assembly file name without extension
-                    else
-                    {
-                        UseExecutableName(Path.GetFileNameWithoutExtension(entryAssemblyLocation));
-                    }
-                }
-                // If location is null then just use a stub
-                else
-                {
-                    UseExecutableName("app");
-                }
-            }
-
-            if (_versionText.IsNullOrWhiteSpace())
-            {
-                // Entry assembly is null in tests
-                UseVersionText(EntryAssembly?.GetName().Version.ToString() ?? "1.0");
-            }
-
-            if (_console == null)
-            {
-                UseConsole(new SystemConsole());
-            }
-
-            if (_commandFactory == null)
-            {
-                UseCommandFactory(new CommandFactory());
-            }
-        }
-
         /// <inheritdoc />
         public ICliApplication Build()
         {
             // Use defaults for required parameters that were not configured
-            SetFallbackValues();
+            _title = _title ?? GetDefaultTitle() ?? "App";
+            _executableName = _executableName ?? GetDefaultExecutableName() ?? "app";
+            _versionText = _versionText ?? GetDefaultVersionText() ?? "v1.0";
+            _console = _console ?? new SystemConsole();
+            _commandFactory = _commandFactory ?? new CommandFactory();
 
             // Project parameters to expected types
             var metadata = new ApplicationMetadata(_title, _executableName, _versionText, _description);
-            var configuration = new ApplicationConfiguration(_commandTypes.ToArray());
+            var configuration = new ApplicationConfiguration(_commandTypes.ToArray(), _isDebugModeAllowed, _isPreviewModeAllowed);
 
             return new CliApplication(metadata, configuration,
                 _console, new CommandInputParser(), new CommandSchemaResolver(),
@@ -159,6 +132,25 @@ namespace CliFx
     {
         private static readonly Lazy<Assembly> LazyEntryAssembly = new Lazy<Assembly>(Assembly.GetEntryAssembly);
 
+        // Entry assembly is null in tests
         private static Assembly EntryAssembly => LazyEntryAssembly.Value;
+
+        private static string GetDefaultTitle() => EntryAssembly?.GetName().Name;
+
+        private static string GetDefaultExecutableName()
+        {
+            var entryAssemblyLocation = EntryAssembly?.Location;
+
+            // If it's a .dll assembly, prepend 'dotnet' and keep the file extension
+            if (string.Equals(Path.GetExtension(entryAssemblyLocation), ".dll", StringComparison.OrdinalIgnoreCase))
+            {
+                return "dotnet " + Path.GetFileName(entryAssemblyLocation);
+            }
+
+            // Otherwise just use assembly file name without extension
+            return Path.GetFileNameWithoutExtension(entryAssemblyLocation);
+        }
+
+        private static string GetDefaultVersionText() => EntryAssembly != null ? $"v{EntryAssembly.GetName().Version}" : null;
     }
 }

CliFx/CliFx.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <TargetFrameworks>net45;netstandard2.0</TargetFrameworks>
     <LangVersion>latest</LangVersion>
-    <Version>0.0.2</Version>
+    <Version>0.0.4</Version>
     <Company>Tyrrrz</Company>
     <Authors>$(Company)</Authors>
     <Copyright>Copyright (C) Alexey Golub</Copyright>

CliFx/Exceptions/CliFxException.cs

@@ -5,12 +5,12 @@ namespace CliFx.Exceptions
     /// <summary>
     /// Domain exception thrown within CliFx.
     /// </summary>
-    public abstract class CliFxException : Exception
+    public class CliFxException : Exception
     {
         /// <summary>
         /// Initializes an instance of <see cref="CliFxException"/>.
         /// </summary>
-        protected CliFxException(string message)
+        public CliFxException(string message)
             : base(message)
         {
         }
@@ -18,7 +18,7 @@ namespace CliFx.Exceptions
         /// <summary>
         /// Initializes an instance of <see cref="CliFxException"/>.
         /// </summary>
-        protected CliFxException(string message, Exception innerException)
+        public CliFxException(string message, Exception innerException)
             : base(message, innerException)
         {
         }

CliFx/Exceptions/CommandException.cs

@@ -8,7 +8,7 @@ namespace CliFx.Exceptions
     /// Use this exception if you want to report an error that occured during execution of a command.
     /// This exception also allows specifying exit code which will be returned to the calling process.
     /// </summary>
-    public class CommandException : CliFxException
+    public class CommandException : Exception
     {
         private const int DefaultExitCode = -100;
 

CliFx/Exceptions/InvalidCommandOptionInputException.cs

@@ -1,26 +0,0 @@
-using System;
-
-namespace CliFx.Exceptions
-{
-    /// <summary>
-    /// Thrown when a command option can't be converted to target type specified in its schema.
-    /// </summary>
-    public class InvalidCommandOptionInputException : CliFxException
-    {
-        /// <summary>
-        /// Initializes an instance of <see cref="InvalidCommandOptionInputException"/>.
-        /// </summary>
-        public InvalidCommandOptionInputException(string message)
-            : base(message)
-        {
-        }
-
-        /// <summary>
-        /// Initializes an instance of <see cref="InvalidCommandOptionInputException"/>.
-        /// </summary>
-        public InvalidCommandOptionInputException(string message, Exception innerException)
-            : base(message, innerException)
-        {
-        }
-    }
-}

CliFx/Exceptions/InvalidCommandSchemaException.cs

@@ -1,26 +0,0 @@
-using System;
-
-namespace CliFx.Exceptions
-{
-    /// <summary>
-    /// Thrown when a command schema fails validation.
-    /// </summary>
-    public class InvalidCommandSchemaException : CliFxException
-    {
-        /// <summary>
-        /// Initializes an instance of <see cref="InvalidCommandSchemaException"/>.
-        /// </summary>
-        public InvalidCommandSchemaException(string message)
-            : base(message)
-        {
-        }
-
-        /// <summary>
-        /// Initializes an instance of <see cref="InvalidCommandSchemaException"/>.
-        /// </summary>
-        public InvalidCommandSchemaException(string message, Exception innerException)
-            : base(message, innerException)
-        {
-        }
-    }
-}

CliFx/Exceptions/MissingCommandOptionInputException.cs

@@ -1,26 +0,0 @@
-using System;
-
-namespace CliFx.Exceptions
-{
-    /// <summary>
-    /// Thrown when a required command option was not set.
-    /// </summary>
-    public class MissingCommandOptionInputException : CliFxException
-    {
-        /// <summary>
-        /// Initializes an instance of <see cref="MissingCommandOptionInputException"/>.
-        /// </summary>
-        public MissingCommandOptionInputException(string message)
-            : base(message)
-        {
-        }
-
-        /// <summary>
-        /// Initializes an instance of <see cref="MissingCommandOptionInputException"/>.
-        /// </summary>
-        public MissingCommandOptionInputException(string message, Exception innerException)
-            : base(message, innerException)
-        {
-        }
-    }
-}

CliFx/ICliApplicationBuilder.cs

@@ -19,6 +19,16 @@ namespace CliFx
         /// </summary>
         ICliApplicationBuilder AddCommandsFrom(Assembly commandAssembly);
 
+        /// <summary>
+        /// Specifies whether debug mode (enabled with [debug] directive) is allowed in the application.
+        /// </summary>
+        ICliApplicationBuilder AllowDebugMode(bool isAllowed = true);
+
+        /// <summary>
+        /// Specifies whether preview mode (enabled with [preview] directive) is allowed in the application.
+        /// </summary>
+        ICliApplicationBuilder AllowPreviewMode(bool isAllowed = true);
+
         /// <summary>
         /// Sets application title, which appears in the help text.
         /// </summary>

CliFx/Internal/Extensions.cs

@@ -26,11 +26,6 @@ namespace CliFx.Internal
         public static StringBuilder AppendIfNotEmpty(this StringBuilder builder, char value) =>
             builder.Length > 0 ? builder.Append(value) : builder;
 
-        public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dic, TKey key) =>
-            dic.TryGetValue(key, out var result) ? result : default;
-
-        public static IEnumerable<T> ExceptNull<T>(this IEnumerable<T> source) where T : class => source.Where(i => i != null);
-
         public static IEnumerable<T> Concat<T>(this IEnumerable<T> source, T value)
         {
             foreach (var i in source)
@@ -51,7 +46,7 @@ namespace CliFx.Internal
 
             return type.GetInterfaces()
                 .Select(GetEnumerableUnderlyingType)
-                .ExceptNull()
+                .Where(t => t != default)
                 .OrderByDescending(t => t != typeof(object)) // prioritize more specific types
                 .FirstOrDefault();
         }

CliFx/Models/ApplicationConfiguration.cs

@@ -10,16 +10,29 @@ namespace CliFx.Models
     public class ApplicationConfiguration
     {
         /// <summary>
-        /// Command types defined in the application.
+        /// Command types defined in this application.
         /// </summary>
         public IReadOnlyList<Type> CommandTypes { get; }
 
+        /// <summary>
+        /// Whether debug mode is allowed in this application.
+        /// </summary>
+        public bool IsDebugModeAllowed { get; }
+
+        /// <summary>
+        /// Whether preview mode is allowed in this application.
+        /// </summary>
+        public bool IsPreviewModeAllowed { get; }
+
         /// <summary>
         /// Initializes an instance of <see cref="ApplicationConfiguration"/>.
         /// </summary>
-        public ApplicationConfiguration(IReadOnlyList<Type> commandTypes)
+        public ApplicationConfiguration(IReadOnlyList<Type> commandTypes,
+            bool isDebugModeAllowed, bool isPreviewModeAllowed)
         {
             CommandTypes = commandTypes.GuardNotNull(nameof(commandTypes));
+            IsDebugModeAllowed = isDebugModeAllowed;
+            IsPreviewModeAllowed = isPreviewModeAllowed;
         }
     }
 }

CliFx/Models/CommandInput.cs

@@ -15,6 +15,11 @@ namespace CliFx.Models
         /// </summary>
         public string CommandName { get; }
 
+        /// <summary>
+        /// Specified directives.
+        /// </summary>
+        public IReadOnlyList<string> Directives { get; }
+
         /// <summary>
         /// Specified options.
         /// </summary>
@@ -23,12 +28,21 @@ namespace CliFx.Models
         /// <summary>
         /// Initializes an instance of <see cref="CommandInput"/>.
         /// </summary>
-        public CommandInput(string commandName, IReadOnlyList<CommandOptionInput> options)
+        public CommandInput(string commandName, IReadOnlyList<string> directives, IReadOnlyList<CommandOptionInput> options)
         {
             CommandName = commandName; // can be null
+            Directives = directives.GuardNotNull(nameof(directives));
             Options = options.GuardNotNull(nameof(options));
         }
 
+        /// <summary>
+        /// Initializes an instance of <see cref="CommandInput"/>.
+        /// </summary>
+        public CommandInput(string commandName, IReadOnlyList<CommandOptionInput> options)
+            : this(commandName, EmptyDirectives, options)
+        {
+        }
+
         /// <summary>
         /// Initializes an instance of <see cref="CommandInput"/>.
         /// </summary>
@@ -41,15 +55,7 @@ namespace CliFx.Models
         /// Initializes an instance of <see cref="CommandInput"/>.
         /// </summary>
         public CommandInput(string commandName)
-            : this(commandName, new CommandOptionInput[0])
-        {
-        }
-
-        /// <summary>
-        /// Initializes an instance of <see cref="CommandInput"/>.
-        /// </summary>
-        public CommandInput()
-            : this(null, new CommandOptionInput[0])
+            : this(commandName, EmptyOptions)
         {
         }
 
@@ -61,6 +67,12 @@ namespace CliFx.Models
             if (!CommandName.IsNullOrWhiteSpace())
                 buffer.Append(CommandName);
 
+            foreach (var directive in Directives)
+            {
+                buffer.AppendIfNotEmpty(' ');
+                buffer.Append(directive);
+            }
+
             foreach (var option in Options)
             {
                 buffer.AppendIfNotEmpty(' ');
@@ -73,9 +85,12 @@ namespace CliFx.Models
 
     public partial class CommandInput
     {
+        private static readonly IReadOnlyList<string> EmptyDirectives = new string[0];
+        private static readonly IReadOnlyList<CommandOptionInput> EmptyOptions = new CommandOptionInput[0];
+
         /// <summary>
         /// Empty input.
         /// </summary>
-        public static CommandInput Empty { get; } = new CommandInput();
+        public static CommandInput Empty { get; } = new CommandInput(EmptyOptions);
     }
 }

CliFx/Models/CommandOptionInput.cs

@@ -7,7 +7,7 @@ namespace CliFx.Models
     /// <summary>
     /// Parsed option from command line input.
     /// </summary>
-    public class CommandOptionInput
+    public partial class CommandOptionInput
     {
         /// <summary>
         /// Specified option alias.
@@ -40,7 +40,7 @@ namespace CliFx.Models
         /// Initializes an instance of <see cref="CommandOptionInput"/>.
         /// </summary>
         public CommandOptionInput(string alias)
-            : this(alias, new string[0])
+            : this(alias, EmptyValues)
         {
         }
 
@@ -70,4 +70,9 @@ namespace CliFx.Models
             return buffer.ToString();
         }
     }
+
+    public partial class CommandOptionInput
+    {
+        private static readonly IReadOnlyList<string> EmptyValues = new string[0];
+    }
 }

CliFx/Models/Extensions.cs

@@ -109,26 +109,42 @@ namespace CliFx.Models
         }
 
         /// <summary>
-        /// Gets whether help was requested in the input.
+        /// Gets whether debug directive was specified in the input.
         /// </summary>
-        public static bool IsHelpRequested(this CommandInput commandInput)
+        public static bool IsDebugDirectiveSpecified(this CommandInput commandInput)
+        {
+            commandInput.GuardNotNull(nameof(commandInput));
+            return commandInput.Directives.Contains("debug", StringComparer.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Gets whether preview directive was specified in the input.
+        /// </summary>
+        public static bool IsPreviewDirectiveSpecified(this CommandInput commandInput)
+        {
+            commandInput.GuardNotNull(nameof(commandInput));
+            return commandInput.Directives.Contains("preview", StringComparer.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Gets whether help option was specified in the input.
+        /// </summary>
+        public static bool IsHelpOptionSpecified(this CommandInput commandInput)
         {
             commandInput.GuardNotNull(nameof(commandInput));
 
             var firstOption = commandInput.Options.FirstOrDefault();
-
             return firstOption != null && CommandOptionSchema.HelpOption.MatchesAlias(firstOption.Alias);
         }
 
         /// <summary>
-        /// Gets whether version information was requested in the input.
+        /// Gets whether version option was specified in the input.
         /// </summary>
-        public static bool IsVersionRequested(this CommandInput commandInput)
+        public static bool IsVersionOptionSpecified(this CommandInput commandInput)
         {
             commandInput.GuardNotNull(nameof(commandInput));
 
             var firstOption = commandInput.Options.FirstOrDefault();
-
             return firstOption != null && CommandOptionSchema.VersionOption.MatchesAlias(firstOption.Alias);
         }
 

CliFx/Services/CommandInitializer.cs

@@ -61,7 +61,7 @@ namespace CliFx.Services
             if (unsetRequiredOptions.Any())
             {
                 var unsetRequiredOptionNames = unsetRequiredOptions.Select(o => o.GetAliases().FirstOrDefault()).JoinToString(", ");
-                throw new MissingCommandOptionInputException($"One or more required options were not set: {unsetRequiredOptionNames}.");
+                throw new CliFxException($"One or more required options were not set: {unsetRequiredOptionNames}.");
             }
         }
     }

CliFx/Services/CommandInputParser.cs

@@ -18,8 +18,10 @@ namespace CliFx.Services
             commandLineArguments.GuardNotNull(nameof(commandLineArguments));
 
             var commandNameBuilder = new StringBuilder();
+            var directives = new List<string>();
             var optionsDic = new Dictionary<string, List<string>>();
 
+            // Option aliases and values are parsed in pairs so we need to keep track of last alias
             var lastOptionAlias = "";
 
             foreach (var commandLineArgument in commandLineArguments)
@@ -34,7 +36,7 @@ namespace CliFx.Services
                         optionsDic[lastOptionAlias] = new List<string>();
                 }
 
-                // Encountered short option name or multiple thereof
+                // Encountered short option name or multiple short option names
                 else if (commandLineArgument.StartsWith("-", StringComparison.OrdinalIgnoreCase))
                 {
                     // Handle stacked options
@@ -48,12 +50,23 @@ namespace CliFx.Services
                     }
                 }
 
-                // Encountered command name or part thereof
+                // Encountered directive or (part of) command name
                 else if (lastOptionAlias.IsNullOrWhiteSpace())
+                {
+                    if (commandLineArgument.StartsWith("[", StringComparison.OrdinalIgnoreCase) &&
+                        commandLineArgument.EndsWith("]", StringComparison.OrdinalIgnoreCase))
+                    {
+                        // Extract directive
+                        var directive = commandLineArgument.Substring(1, commandLineArgument.Length - 2);
+
+                        directives.Add(directive);
+                    }
+                    else
                     {
                         commandNameBuilder.AppendIfNotEmpty(' ');
                         commandNameBuilder.Append(commandLineArgument);
                     }
+                }
 
                 // Encountered option value
                 else if (!lastOptionAlias.IsNullOrWhiteSpace())
@@ -65,7 +78,7 @@ namespace CliFx.Services
             var commandName = commandNameBuilder.Length > 0 ? commandNameBuilder.ToString() : null;
             var options = optionsDic.Select(p => new CommandOptionInput(p.Key, p.Value)).ToArray();
 
-            return new CommandInput(commandName, options);
+            return new CommandInput(commandName, directives, options);
         }
     }
 }

CliFx/Services/CommandOptionInputConverter.cs

@@ -127,11 +127,11 @@ namespace CliFx.Services
                 if (parseMethod != null)
                     return parseMethod.Invoke(null, new object[] {value});
 
-                throw new InvalidCommandOptionInputException($"Can't convert value [{value}] to type [{targetType}].");
+                throw new CliFxException($"Can't convert value [{value}] to type [{targetType}].");
             }
             catch (Exception ex)
             {
-                throw new InvalidCommandOptionInputException($"Can't convert value [{value}] to type [{targetType}].", ex);
+                throw new CliFxException($"Can't convert value [{value}] to type [{targetType}].", ex);
             }
         }
 
@@ -166,7 +166,7 @@ namespace CliFx.Services
                 if (arrayConstructor != null)
                     return arrayConstructor.Invoke(new object[] {convertedValues});
 
-                throw new InvalidCommandOptionInputException(
+                throw new CliFxException(
                     $"Can't convert sequence of values [{optionInput.Values.JoinToString(", ")}] to type [{targetType}].");
             }
         }

CliFx/Services/CommandSchemaResolver.cs

@@ -14,31 +14,54 @@ namespace CliFx.Services
     /// </summary>
     public class CommandSchemaResolver : ICommandSchemaResolver
     {
-        private CommandOptionSchema GetCommandOptionSchema(PropertyInfo optionProperty)
+        private IReadOnlyList<CommandOptionSchema> GetCommandOptionSchemas(Type commandType)
         {
-            var attribute = optionProperty.GetCustomAttribute<CommandOptionAttribute>();
+            var result = new List<CommandOptionSchema>();
 
+            foreach (var property in commandType.GetProperties())
+            {
+                var attribute = property.GetCustomAttribute<CommandOptionAttribute>();
+
+                // If an attribute is not set, then it's not an option so we just skip it
                 if (attribute == null)
-                return null;
+                    continue;
 
-            return new CommandOptionSchema(optionProperty,
+                // Build option schema
+                var optionSchema = new CommandOptionSchema(property,
                     attribute.Name,
                     attribute.ShortName,
                     attribute.IsRequired,
                     attribute.Description);
+
+                // Make sure there are no other options with the same name
+                var existingOptionWithSameName = result
+                    .Where(o => !o.Name.IsNullOrWhiteSpace())
+                    .FirstOrDefault(o => string.Equals(o.Name, optionSchema.Name, StringComparison.OrdinalIgnoreCase));
+
+                if (existingOptionWithSameName != null)
+                {
+                    throw new CliFxException(
+                        $"Command type [{commandType}] has options defined with the same name: " +
+                        $"[{existingOptionWithSameName.Property}] and [{optionSchema.Property}].");
                 }
 
-        private CommandSchema GetCommandSchema(Type commandType)
+                // Make sure there are no other options with the same short name
+                var existingOptionWithSameShortName = result
+                    .Where(o => o.ShortName != null)
+                    .FirstOrDefault(o => o.ShortName == optionSchema.ShortName);
+
+                if (existingOptionWithSameShortName != null)
                 {
-            // Attribute is optional for commands in order to reduce runtime rule complexity
-            var attribute = commandType.GetCustomAttribute<CommandAttribute>();
+                    throw new CliFxException(
+                        $"Command type [{commandType}] has options defined with the same short name: " +
+                        $"[{existingOptionWithSameShortName.Property}] and [{optionSchema.Property}].");
+                }
 
-            var options = commandType.GetProperties().Select(GetCommandOptionSchema).ExceptNull().ToArray();
+                // Add schema to list
+                result.Add(optionSchema);
+            }
 
-            return new CommandSchema(commandType,
-                attribute?.Name,
-                attribute?.Description,
-                options);
+            return result;
         }
 
         /// <inheritdoc />
@@ -46,82 +69,55 @@ namespace CliFx.Services
         {
             commandTypes.GuardNotNull(nameof(commandTypes));
 
-            // Get command schemas
-            var commandSchemas = commandTypes.Select(GetCommandSchema).ToArray();
-
-            // Throw if there are no commands defined
-            if (!commandSchemas.Any())
+            // Make sure there's at least one command defined
+            if (!commandTypes.Any())
             {
-                throw new InvalidCommandSchemaException("There are no commands defined.");
+                throw new CliFxException("There are no commands defined.");
             }
 
-            // Throw if there are multiple commands with the same name
-            var nonUniqueCommandNames = commandSchemas
-                .Select(c => c.Name)
-                .GroupBy(i => i, StringComparer.OrdinalIgnoreCase)
-                .Where(g => g.Count() >= 2)
-                .SelectMany(g => g)
-                .Distinct(StringComparer.OrdinalIgnoreCase)
-                .ToArray();
+            var result = new List<CommandSchema>();
 
-            foreach (var commandName in nonUniqueCommandNames)
+            foreach (var commandType in commandTypes)
             {
-                throw new InvalidCommandSchemaException(!commandName.IsNullOrWhiteSpace()
-                    ? $"There are multiple commands defined with name [{commandName}]."
-                    : "There are multiple default commands defined.");
+                // Make sure command type implements ICommand.
+                if (!commandType.Implements(typeof(ICommand)))
+                {
+                    throw new CliFxException($"Command type [{commandType}] must implement {typeof(ICommand)}.");
                 }
 
-            // Throw if there are commands that don't implement ICommand
-            var nonImplementedCommandNames = commandSchemas
-                .Where(c => !c.Type.Implements(typeof(ICommand)))
-                .Select(c => c.Name)
-                .Distinct(StringComparer.OrdinalIgnoreCase)
-                .ToArray();
+                // Get attribute
+                var attribute = commandType.GetCustomAttribute<CommandAttribute>();
 
-            foreach (var commandName in nonImplementedCommandNames)
+                // Make sure attribute is set
+                if (attribute == null)
                 {
-                throw new InvalidCommandSchemaException(!commandName.IsNullOrWhiteSpace()
-                    ? $"Command [{commandName}] doesn't implement ICommand."
-                    : "Default command doesn't implement ICommand.");
+                    throw new CliFxException($"Command type [{commandType}] must be annotated with [{typeof(CommandAttribute)}].");
                 }
 
-            // Throw if there are multiple options with the same name inside the same command
-            foreach (var commandSchema in commandSchemas)
-            {
-                var nonUniqueOptionNames = commandSchema.Options
-                    .Where(o => !o.Name.IsNullOrWhiteSpace())
-                    .Select(o => o.Name)
-                    .GroupBy(i => i, StringComparer.OrdinalIgnoreCase)
-                    .Where(g => g.Count() >= 2)
-                    .SelectMany(g => g)
-                    .Distinct(StringComparer.OrdinalIgnoreCase)
-                    .ToArray();
+                // Get option schemas
+                var optionSchemas = GetCommandOptionSchemas(commandType);
 
-                foreach (var optionName in nonUniqueOptionNames)
+                // Build command schema
+                var commandSchema = new CommandSchema(commandType,
+                    attribute.Name,
+                    attribute.Description,
+                    optionSchemas);
+
+                // Make sure there are no other commands with the same name
+                var existingCommandWithSameName = result
+                    .FirstOrDefault(c => string.Equals(c.Name, commandSchema.Name, StringComparison.OrdinalIgnoreCase));
+
+                if (existingCommandWithSameName != null)
                 {
-                    throw new InvalidCommandSchemaException(!commandSchema.Name.IsNullOrWhiteSpace()
-                        ? $"There are multiple options defined with name [{optionName}] on command [{commandSchema.Name}]."
-                        : $"There are multiple options defined with name [{optionName}] on default command.");
+                    throw new CliFxException(
+                        $"Command type [{existingCommandWithSameName.Type}] has the same name as another command type [{commandType}].");
                 }
 
-                var nonUniqueOptionShortNames = commandSchema.Options
-                    .Where(o => o.ShortName != null)
-                    .Select(o => o.ShortName.Value)
-                    .GroupBy(i => i)
-                    .Where(g => g.Count() >= 2)
-                    .SelectMany(g => g)
-                    .Distinct()
-                    .ToArray();
-
-                foreach (var optionShortName in nonUniqueOptionShortNames)
-                {
-                    throw new InvalidCommandSchemaException(!commandSchema.Name.IsNullOrWhiteSpace()
-                        ? $"There are multiple options defined with short name [{optionShortName}] on command [{commandSchema.Name}]."
-                        : $"There are multiple options defined with short name [{optionShortName}] on default command.");
-                }
+                // Add schema to list
+                result.Add(commandSchema);
             }
 
-            return commandSchemas;
+            return result;
         }
     }
 }

CliFx/Services/HelpTextRenderer.cs

@@ -169,8 +169,14 @@ namespace CliFx.Services
                 // Header
                 RenderHeader("Options");
 
+                // Order options and append built-in options
+                var allOptionSchemas = source.TargetCommandSchema.Options
+                    .OrderByDescending(o => o.IsRequired)
+                    .Concat(builtInOptionSchemas)
+                    .ToArray();
+
                 // Options
-                foreach (var optionSchema in source.TargetCommandSchema.Options.Concat(builtInOptionSchemas))
+                foreach (var optionSchema in allOptionSchemas)
                 {
                     // Is required
                     if (optionSchema.IsRequired)

CliFx/Services/ICommandFactory.cs

@@ -1,5 +1,4 @@
-using System;
-using CliFx.Models;
+using CliFx.Models;
 
 namespace CliFx.Services
 {

CliFx/Services/VirtualConsole.cs

@@ -15,19 +15,19 @@ namespace CliFx.Services
         public TextReader Input { get; }
 
         /// <inheritdoc />
-        public bool IsInputRedirected => true;
+        public bool IsInputRedirected { get; }
 
         /// <inheritdoc />
         public TextWriter Output { get; }
 
         /// <inheritdoc />
-        public bool IsOutputRedirected => true;
+        public bool IsOutputRedirected { get; }
 
         /// <inheritdoc />
         public TextWriter Error { get; }
 
         /// <inheritdoc />
-        public bool IsErrorRedirected => true;
+        public bool IsErrorRedirected { get; }
 
         /// <inheritdoc />
         public ConsoleColor ForegroundColor { get; set; } = ConsoleColor.Gray;
@@ -38,11 +38,24 @@ namespace CliFx.Services
         /// <summary>
         /// Initializes an instance of <see cref="VirtualConsole"/>.
         /// </summary>
-        public VirtualConsole(TextReader input, TextWriter output, TextWriter error)
+        public VirtualConsole(TextReader input, bool isInputRedirected,
+            TextWriter output, bool isOutputRedirected,
+            TextWriter error, bool isErrorRedirected)
         {
             Input = input.GuardNotNull(nameof(input));
+            IsInputRedirected = isInputRedirected;
             Output = output.GuardNotNull(nameof(output));
+            IsOutputRedirected = isOutputRedirected;
             Error = error.GuardNotNull(nameof(error));
+            IsErrorRedirected = isErrorRedirected;
+        }
+
+        /// <summary>
+        /// Initializes an instance of <see cref="VirtualConsole"/>.
+        /// </summary>
+        public VirtualConsole(TextReader input, TextWriter output, TextWriter error)
+            : this(input, true, output, true, error, true)
+        {
         }
 
         /// <summary>

CliFx/Utilities/Extensions.cs

@@ -0,0 +1,15 @@
+using CliFx.Services;
+
+namespace CliFx.Utilities
+{
+    /// <summary>
+    /// Extensions for <see cref="Utilities"/>.
+    /// </summary>
+    public static class Extensions
+    {
+        /// <summary>
+        /// Creates a <see cref="ProgressTicker"/> bound to this console.
+        /// </summary>
+        public static ProgressTicker CreateProgressTicker(this IConsole console) => new ProgressTicker(console);
+    }
+}

CliFx/Utilities/ProgressTicker.cs

@@ -0,0 +1,50 @@
+using System;
+using CliFx.Services;
+
+namespace CliFx.Utilities
+{
+    /// <summary>
+    /// Utility for rendering current progress to the console that erases and rewrites output on every tick.
+    /// </summary>
+    public class ProgressTicker : IProgress<double>
+    {
+        private readonly IConsole _console;
+
+        private string _lastOutput = "";
+
+        /// <summary>
+        /// Initializes an instance of <see cref="ProgressTicker"/>.
+        /// </summary>
+        public ProgressTicker(IConsole console)
+        {
+            _console = console;
+        }
+
+        private void EraseLastOutput()
+        {
+            for (var i = 0; i < _lastOutput.Length; i++)
+                _console.Output.Write('\b');
+        }
+
+        private void RenderProgress(double progress)
+        {
+            _lastOutput = progress.ToString("P2", _console.Output.FormatProvider);
+            _console.Output.Write(_lastOutput);
+        }
+
+        /// <summary>
+        /// Erases previous output and renders new progress to the console.
+        /// If console's stdout is redirected, this method returns without doing anything.
+        /// </summary>
+        public void Report(double progress)
+        {
+            // We don't do anything if stdout is redirected to avoid polluting output
+            //...when there's no active console window.
+            if (!_console.IsOutputRedirected)
+            {
+                EraseLastOutput();
+                RenderProgress(progress);
+            }
+        }
+    }
+}

Readme.md

@@ -21,21 +21,30 @@ _CliFx is to command line interfaces what ASP.NET Core is to web applications._
 
 - Complete application framework, not just an argument parser
 - Requires minimal amount of code to get started
-- Resolves commands using attributes
+- Resolves commands and options using attributes
 - Handles options of various types, including custom types
 - Supports multi-level command hierarchies
 - Generates contextual help text
 - Prints errors and routes exit codes on exceptions
-- Highly testable and easy to customize
+- Highly testable and easy to debug
 - Targets .NET Framework 4.5+ and .NET Standard 2.0+
 - No external dependencies
 
-### Currently not implemented
+## Argument syntax
 
-- Positional arguments (anonymous options)
-- Auto-completion support
-- Environment variables
-- Runtime directives
+This library employs a variation of the GNU command line argument syntax. Because CliFx uses a context-unaware parser, the syntax rules are generally more consistent and intuitive.
+
+The following examples are valid for any application created with CliFx:
+
+- `myapp --foo bar` sets option `"foo"` to value `"bar"`
+- `myapp -f bar` sets option `'f'` to value `"bar"`
+- `myapp --switch` sets option `"switch"` to value `true` 
+- `myapp -s` sets option `'s'` to value `true` 
+- `myapp -abc` sets options `'a'`, `'b'` and `'c'` to value `true`
+- `myapp -xqf bar` sets options `'x'` and `'q'` to value `true`, and option `'f'` to value `"bar"`
+- `myapp -i file1.txt file2.txt` sets option `'i'` to a sequence of values `"file1.txt"` and `"file2.txt"`
+- `myapp -i file1.txt -i file2.txt` sets option `'i'` to a sequence of values `"file1.txt"` and `"file2.txt"`
+- `myapp jar new -o cookie` invokes command `jar new` and sets option `'o'` to value `"cookie"`
 
 ## Usage
 
@@ -262,6 +271,21 @@ var app = new CliApplicationBuilder()
     .Build();
 ```
 
+### Report progress
+
+CliFx comes with a simple utility for reporting progress to the console, `ProgressTicker`, which renders progress in-place on every tick.
+
+It implements a well-known `IProgress<double>` interface so you can pass it to methods that are aware of this abstraction.
+
+To avoid polluting output when it's not bound to a console, `ProgressTicker` will simply no-op if stdout is redirected.
+
+```c#
+var progressTicker = console.CreateProgressTicker();
+
+for (var i = 0.0; i <= 1; i += 0.01)
+    progressTicker.Report(i);
+```
+
 ### Testing
 
 CliFx makes it really easy to test your commands thanks to the `IConsole` interface.
@@ -344,6 +368,24 @@ public async Task ConcatCommand_Test()
 }
 ```
 
+### Debug and preview mode
+
+When troubleshooting issues, you may find it useful to run your app in debug or preview mode. To do it, simply pass the corresponding directive to your app along with other command line arguments, e.g.: `myapp [debug] user add -n "John Doe" -e john.doe@example.com`
+
+If your application is ran in debug mode (`[debug]` directive), it will wait for debugger to be attached before proceeding. This is useful for debugging apps that were ran outside of your IDE.
+
+If preview mode is specified (`[preview]` directive), the app will print consumed command line arguments as they were parsed. This is useful when troubleshooting issues related to option parsing.
+
+You can also disallow these directives, e.g. when running in production, by calling `AllowDebugMode` and `AllowPreviewMode` methods on `CliApplicationBuilder`.
+
+```c#
+var app = new CliApplicationBuilder()
+    .AddCommandsFromThisAssembly()
+    .AllowDebugMode(true) // allow debug mode
+    .AllowPreviewMode(false) // disallow preview mode
+    .Build();
+```
+
 ## Benchmarks
 
 CliFx has the smallest performance overhead compared to other command line parsers and frameworks.
@@ -394,7 +436,6 @@ CliFx is made out of "Cli" for "Command Line Interface" and "Fx" for "Framework"
 ## Libraries used
 
 - [NUnit](https://github.com/nunit/nunit)
-- [CliWrap](https://github.com/Tyrrrz/CliWrap)
 - [FluentAssertions](https://github.com/fluentassertions/fluentassertions)
 - [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json)
 - [BenchmarkDotNet](https://github.com/dotnet/BenchmarkDotNet)