Add dummy tests to cover difficult scenarios

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

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="../CliFx.props" />
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\CliFx\CliFx.csproj" />
+  </ItemGroup>
+
+</Project>

CliFx.Tests.Dummy/Commands/HelloWorldCommand.cs

@@ -0,0 +1,19 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+
+namespace CliFx.Tests.Dummy.Commands
+{
+    [Command]
+    public class HelloWorldCommand : ICommand
+    {
+        [CommandOption("target", EnvironmentVariableName = "ENV_TARGET")]
+        public string Target { get; set; } = "World";
+
+        public ValueTask ExecuteAsync(IConsole console)
+        {
+            console.Output.WriteLine($"Hello {Target}!");
+
+            return default;
+        }
+    }
+}

CliFx.Tests.Dummy/Program.cs

@@ -0,0 +1,13 @@
+using System.Threading.Tasks;
+
+namespace CliFx.Tests.Dummy
+{
+    public class Program
+    {
+        public static async Task Main() =>
+            await new CliApplicationBuilder()
+                .AddCommandsFromThisAssembly()
+                .Build()
+                .RunAsync();
+    }
+}

CliFx.Tests/CliFx.Tests.csproj

@@ -11,6 +11,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="CliWrap" Version="2.5.0" />
     <PackageReference Include="FluentAssertions" Version="5.10.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
     <PackageReference Include="NUnit" Version="3.12.0" />
@@ -19,7 +20,12 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\CliFx.Tests.Dummy\CliFx.Tests.Dummy.csproj" />
     <ProjectReference Include="..\CliFx\CliFx.csproj" />
   </ItemGroup>
 
+  <Target Name="Copy dummy's runtime config" AfterTargets="AfterBuild">
+    <Copy SourceFiles="../CliFx.Tests.Dummy/bin/$(Configuration)/$(TargetFramework)/CliFx.Tests.Dummy.runtimeconfig.json" DestinationFiles="$(OutputPath)CliFx.Tests.Dummy.runtimeconfig.json" />
+  </Target>
+
 </Project>

CliFx.Tests/DummyTests.cs

@@ -0,0 +1,82 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Threading.Tasks;
+using CliWrap;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace CliFx.Tests
+{
+    [TestFixture]
+    public class DummyTests
+    {
+        private static Assembly DummyAssembly { get; } = typeof(Dummy.Program).Assembly;
+
+        private static IEnumerable<TestCaseData> GetTestCases_RunAsync()
+        {
+            yield return new TestCaseData(
+                new[] {"--version"},
+                new Dictionary<string, string>(),
+                $"v{DummyAssembly.GetName().Version}"
+            );
+
+            yield return new TestCaseData(
+                new string[0],
+                new Dictionary<string, string>(),
+                "Hello World!"
+            );
+
+            yield return new TestCaseData(
+                new[] {"--target", "Earth"},
+                new Dictionary<string, string>(),
+                "Hello Earth!"
+            );
+
+            yield return new TestCaseData(
+                new string[0],
+                new Dictionary<string, string>
+                {
+                    ["ENV_TARGET"] = "Mars"
+                },
+                "Hello Mars!"
+            );
+
+            yield return new TestCaseData(
+                new[] {"--target", "Earth"},
+                new Dictionary<string, string>
+                {
+                    ["ENV_TARGET"] = "Mars"
+                },
+                "Hello Earth!"
+            );
+        }
+
+        [TestCaseSource(nameof(GetTestCases_RunAsync))]
+        public async Task RunAsync_Test(
+            IReadOnlyList<string> arguments,
+            IReadOnlyDictionary<string, string> environmentVariables,
+            string expectedStdOut)
+        {
+            // Arrange
+            var cli = Cli.Wrap("dotnet")
+                .SetArguments(arguments.Prepend(DummyAssembly.Location).ToArray())
+                .EnableExitCodeValidation()
+                .EnableStandardErrorValidation()
+                .SetStandardOutputCallback(Console.WriteLine)
+                .SetStandardErrorCallback(Console.WriteLine);
+
+            foreach (var (key, value) in environmentVariables)
+                cli.SetEnvironmentVariable(key, value);
+
+            // Act
+            var result = await cli.ExecuteAsync();
+
+            // Assert
+            result.ExitCode.Should().Be(0);
+            result.StandardError.Should().BeNullOrWhiteSpace();
+            result.StandardOutput.TrimEnd().Should().Be(expectedStdOut);
+        }
+    }
+}

CliFx.sln

@@ -19,6 +19,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Benchmarks", "CliFx.B
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CliFx.Demo", "CliFx.Demo\CliFx.Demo.csproj", "{AAB6844C-BF71-448F-A11B-89AEE459AB15}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CliFx.Tests.Dummy", "CliFx.Tests.Dummy\CliFx.Tests.Dummy.csproj", "{F717347D-8656-44DA-A4A2-BE515E8C4655}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -77,6 +79,18 @@ Global
 		{AAB6844C-BF71-448F-A11B-89AEE459AB15}.Release|x64.Build.0 = Release|Any CPU
 		{AAB6844C-BF71-448F-A11B-89AEE459AB15}.Release|x86.ActiveCfg = Release|Any CPU
 		{AAB6844C-BF71-448F-A11B-89AEE459AB15}.Release|x86.Build.0 = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|x64.Build.0 = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Debug|x86.Build.0 = Debug|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|x64.ActiveCfg = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|x64.Build.0 = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|x86.ActiveCfg = Release|Any CPU
+		{F717347D-8656-44DA-A4A2-BE515E8C4655}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE