feat: add snapshot tests

test/Mediator.SourceGenerator.Roslyn38.Tests/Fixture.cs

@@ -51,6 +51,19 @@ public static Compilation CreateLibrary(params string[] source)
         return compilation;
     }
 
+    public static Task VerifyGenerator(string source)
+    {
+        var compilation = CreateLibrary(source);
+
+        var generator = new MediatorGenerator();
+        var driver = CSharpGeneratorDriver.Create(generator);
+
+        var ranDriver = driver.RunGenerators(compilation);
+        var verify = VerifyXunit.Verifier.Verify(ranDriver);
+
+        return verify.ToTask();
+    }
+
     public static Task<string> SourceFromResourceFile(string file) =>
         File.ReadAllTextAsync(Path.Combine("resources", file));
 }

test/Mediator.SourceGenerator.Roslyn38.Tests/Mediator.SourceGenerator.Roslyn38.Tests.csproj

@@ -12,8 +12,12 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="System.Collections.Immutable" Version="7.0.0" />
+    <PackageReference Include="Verify.DiffPlex" Version="2.3.0" />
+    <PackageReference Include="Verify.SourceGenerators" Version="2.2.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="Verify.Xunit" Version="22.1.4" />
+    <PackageReference Include="xunit" Version="2.5.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
@@ -43,6 +47,10 @@
     <None Include="resources\*.cs">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <Compile Remove="_snapshots\**" />
+    <None Include="_snapshots\*.cs">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
   <ItemGroup>

test/Mediator.SourceGenerator.Roslyn38.Tests/ModuleInitializer.cs

@@ -0,0 +1,22 @@
+using System.IO;
+using VerifyTests;
+using VerifyXunit;
+
+namespace Mediator.SourceGenerator.Tests;
+
+public static class ModuleInitializer
+{
+    // ModuleInitializer should only be used in apps
+#pragma warning disable CA2255
+    [ModuleInitializer]
+#pragma warning restore CA2255
+    public static void Init()
+    {
+        Verifier.DerivePathInfo(
+            (file, _, type, method) => new(Path.Join(Path.GetDirectoryName(file), "_snapshots"), type.Name, method.Name)
+        );
+
+        VerifySourceGenerators.Initialize();
+        VerifyDiffPlex.Initialize(VerifyTests.DiffPlex.OutputType.Compact);
+    }
+}

test/Mediator.SourceGenerator.Roslyn38.Tests/SnapshotTests.cs

@@ -0,0 +1,40 @@
+using System.Threading.Tasks;
+using VerifyXunit;
+
+namespace Mediator.SourceGenerator.Tests;
+
+[UsesVerify]
+public sealed class SnapshotTests
+{
+    [Fact]
+    public async Task Test_SimpleConsole()
+    {
+        var source = await Fixture.SourceFromResourceFile("SimpleConsoleProgram.cs");
+
+        await Fixture.VerifyGenerator(source);
+    }
+
+    [Fact]
+    public async Task Test_SimpleEndToEnd()
+    {
+        var source = await Fixture.SourceFromResourceFile("SimpleEndToEndProgram.cs");
+
+        await Fixture.VerifyGenerator(source);
+    }
+
+    [Fact]
+    public async Task Test_SimpleStreaming()
+    {
+        var source = await Fixture.SourceFromResourceFile("SimpleStreamingProgram.cs");
+
+        await Fixture.VerifyGenerator(source);
+    }
+
+    [Fact]
+    public async Task Test_Multiple_AddMediator_Calls()
+    {
+        var source = await Fixture.SourceFromResourceFile("MultipleAddMediatorCalls.cs");
+
+        await Fixture.VerifyGenerator(source);
+    }
+}