docs: add Moq, NSubstitute, and FakeItEasy migration guides for TUnit.Mocks

docs/docs/writing-tests/mocking/index.md

@@ -210,3 +210,4 @@ See [Argument Matchers](argument-matchers) for the full API.
 - [Advanced Features](advanced) — state machines, events, auto-mocking, diagnostics, and more
 - [HTTP Mocking](http) — mock `HttpClient` with `MockHttpHandler`
 - [Logging](logging) — capture and verify `ILogger` calls with `MockLogger`
+- Migrating from another library — [Moq](../../migration/mocking/moq.md), [NSubstitute](../../migration/mocking/nsubstitute.md), or [FakeItEasy](../../migration/mocking/fakeiteasy.md)

docs/sidebars.ts

@@ -227,6 +227,16 @@ const sidebars: SidebarsConfig = {
         'migration/xunit',
         'migration/nunit',
         'migration/mstest',
+        {
+          type: 'category',
+          label: 'Mocking Libraries',
+          collapsed: true,
+          items: [
+            'migration/mocking/moq',
+            'migration/mocking/nsubstitute',
+            'migration/mocking/fakeiteasy',
+          ],
+        },
       ],
     },
     {

skills/tunit/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: tunit
-description: Write or troubleshoot tests using TUnit, TUnit.Assertions, or TUnit.Mocks, or migrate tests to TUnit. Routes to task-specific official documentation. Use only for tasks involving these packages or migration to TUnit.
+description: Write or troubleshoot tests using TUnit, TUnit.Assertions, or TUnit.Mocks, or migrate tests or mocks to TUnit or TUnit.Mocks. Routes to task-specific official documentation. Use only for tasks involving these packages or migration to them.
 license: MIT
 ---
 
@@ -32,6 +32,7 @@ Choose the link that matches the task; these are alternatives, not a reading che
 | Run tests or select tests | [Running tests](https://tunit.dev/docs/getting-started/running-your-tests.md) or [filters](https://tunit.dev/docs/execution/test-filters.md) |
 | Migrate an existing suite | [xUnit](https://tunit.dev/docs/migration/xunit.md), [NUnit](https://tunit.dev/docs/migration/nunit.md), or [MSTest](https://tunit.dev/docs/migration/mstest.md), matching the source framework |
 | Mocking | [TUnit.Mocks](https://tunit.dev/docs/writing-tests/mocking.md) |
+| Migrate mocks to TUnit.Mocks | [Moq](https://tunit.dev/docs/migration/mocking/moq.md), [NSubstitute](https://tunit.dev/docs/migration/mocking/nsubstitute.md), or [FakeItEasy](https://tunit.dev/docs/migration/mocking/fakeiteasy.md), matching the source library |
 | Aspire integration testing | [Aspire](https://tunit.dev/docs/examples/aspire.md) |
 | ASP.NET Core integration testing | [ASP.NET Core](https://tunit.dev/docs/examples/aspnet.md) |
 | Playwright browser testing | [Playwright](https://tunit.dev/docs/examples/playwright.md) |

tests/TUnit.DocTests/TUnit.DocTests.csproj

@@ -38,13 +38,15 @@
     <PackageReference Include="BenchmarkDotNet" />
     <PackageReference Include="bunit" />
     <PackageReference Include="CliWrap" />
+    <PackageReference Include="FakeItEasy" />
     <PackageReference Include="FsCheck" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" />
     <PackageReference Include="Microsoft.EntityFrameworkCore" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
     <PackageReference Include="Microsoft.Playwright" />
+    <PackageReference Include="Moq" />
     <PackageReference Include="MSTest.TestFramework" />
     <PackageReference Include="NSubstitute" />
     <PackageReference Include="NUnit" />

tools/TUnit.DocSnippetGenerator/Program.cs

@@ -436,6 +436,7 @@ static string GenerateSource(
         else
         {
             builder.AppendLine($"namespace {generatedNamespace};");
+            AppendMockingLibraryUsings(builder, snippet);
         }
 
         builder.AppendLine($"#line {snippet.Line} \"{snippet.SourcePath}\"")
@@ -504,6 +505,7 @@ static string GenerateSource(
     }
 
     builder.AppendLine($"namespace {generatedNamespace};");
+    AppendMockingLibraryUsings(builder, snippet);
 
     if (containsExtensionMethod)
     {
@@ -691,6 +693,36 @@ static void AppendFrameworkAliases(StringBuilder builder, Snippet snippet)
     }
 }
 
+// Mocking-library migration pages compare Moq, NSubstitute, and FakeItEasy with TUnit.Mocks.
+// Their type names (Mock<T>, Times, MockBehavior, Arg) clash with TUnit.Mocks' global usings,
+// so a fence marked with the library's name imports it inside the namespace, where lookup
+// finds it before the global usings.
+static void AppendMockingLibraryUsings(StringBuilder builder, Snippet snippet)
+{
+    if (!snippet.SourcePath.Contains("/migration/mocking/", StringComparison.OrdinalIgnoreCase))
+    {
+        return;
+    }
+
+    var marker = Regex.Match(snippet.Source, @"(?m)^\s*//\s*(Moq|NSubstitute|FakeItEasy)\s*$");
+    if (!marker.Success)
+    {
+        return;
+    }
+
+    var namespaces = marker.Groups[1].Value switch
+    {
+        "Moq" => new[] { "Moq" },
+        "NSubstitute" => new[] { "NSubstitute", "NSubstitute.ExceptionExtensions", "NSubstitute.ReceivedExtensions" },
+        _ => new[] { "FakeItEasy" }
+    };
+
+    foreach (var ns in namespaces)
+    {
+        builder.AppendLine($"using {ns};");
+    }
+}
+
 static string QualifyLocallyDeclaredAttributeTypes(string attribute, string source, string generatedNamespace)
 {
     var declaredTypes = Regex.Matches(