Moq.AutoMocker Source Generators

Moq.AutoMock includes built-in source generators that provide compile-time code generation to enhance your testing experience. These generators automatically create boilerplate test code and extension methods, saving you time and reducing repetitive testing code.

Available Generators

Moq.AutoMock includes several source generators:

1. Unit Test Generator

Automatically generates constructor null-check tests for your classes.

Key Features:

• Generates tests for each nullable constructor parameter
• Supports MSTest, xUnit, NUnit, and TUnit testing frameworks
• Validates ArgumentNullException is thrown with correct parameter names
• Provides customization hooks for test setup

Quick Example:

[TestClass]
[ConstructorTests(TargetType = typeof(MyController))]
public partial class MyControllerTests
{
}

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2. Options Extension Generator

Generates WithOptions<T>() extension method when Microsoft.Extensions.Options is referenced.

Key Features:

• Fluent API for configuring options in tests
• Sets up complete options infrastructure (IOptionsMonitor, IOptionsSnapshot, etc.)
• Simplifies testing of classes that depend on IOptions<T>

Quick Example:

mocker.WithOptions<MySettings>(options => 
{
    options.Number = 42;
    options.Required = "test value";
});

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3. Fake Logging Extension Generator

Generates WithFakeLogging() extension method when Microsoft.Extensions.Diagnostics.Testing is referenced.

Key Features:

• Captures log messages for verification
• Uses Microsoft's official testing helpers
• Enables logging behavior validation in tests

Quick Example:

mocker.WithFakeLogging();
var provider = mocker.Get<FakeLoggerProvider>();

// ... perform actions ...

var logs = provider.Collector.GetSnapshot();
Assert.IsTrue(logs.Any(log => log.Message == "Expected message"));

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4. Application Insights Extension Generator

Generates WithApplicationInsights() and related extension methods when Microsoft.ApplicationInsights is referenced. Supports both 2.x and 3.x versions of Application Insights.

Key Features:

• Application Insights 2.x: Uses a FakeTelemetryChannel with GetSentTelemetry() to capture ITelemetry items
• Application Insights 3.x: Uses OpenTelemetry in-memory exporters with GetApplicationInsightsLogRecords(), GetApplicationInsightsMetrics(), and GetApplicationInsightsActivities()

Quick Example (3.x):

mocker.WithApplicationInsights();
var service = mocker.CreateInstance<MyService>();
service.DoWork();

var logRecords = mocker.GetApplicationInsightsLogRecords();
Assert.HasCount(2, logRecords);

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5. Keyed Services Extension Generator

Generates WithKeyedService<T>() extension methods when Microsoft.Extensions.DependencyInjection is referenced.

Key Features:

• Enables testing of keyed services via IKeyedServiceProvider
• Supports [FromKeyedServices] attribute resolution
• Provides both eager and lazy service registration
• Integrates seamlessly with dependency injection

Quick Example:

mocker.WithKeyedService(Mock.Of<IEmailSender>(), "primary");
mocker.WithKeyedService<ICache, RedisCache>("cache");

var service = mocker.CreateInstance<MyService>();
// Keyed services are automatically resolved

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6. Meter Factory Extension Generator

Generates WithMeterFactory() extension method when System.Diagnostics.DiagnosticSource 10.0+ is referenced.

Key Features:

• Provides a real IMeterFactory implementation for metrics testing
• Forwards Create(MeterOptions) directly to new Meter(options)
• Tracks and disposes created meters on cleanup

Quick Example:

mocker.WithMeterFactory();
var service = mocker.CreateInstance<MetricsService>();
// IMeterFactory is automatically resolved with a working implementation

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7. Fake Time Provider Extension Generator

Generates WithFakeTimeProvider() extension method when Microsoft.Extensions.TimeProvider.Testing is referenced.

Key Features:

• Provides a FakeTimeProvider for deterministic time-based testing
• Registers as both TimeProvider (for injection) and FakeTimeProvider (for test control)
• Allows advancing time with Advance() and SetUtcNow()

Quick Example:

mocker.WithFakeTimeProvider();
var fakeTime = mocker.Get<FakeTimeProvider>();
fakeTime.SetUtcNow(new DateTimeOffset(2025, 1, 1, 0, 0, 0, TimeSpan.Zero));

var service = mocker.CreateInstance<MyTimeSensitiveService>();
fakeTime.Advance(TimeSpan.FromHours(1));
// Verify behavior at specific time

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Important: Generated Classes Are Internal Partials

All extension classes created by these source generators are generated as partial classes with internal visibility. For example, the Keyed Services generator produces:

internal static partial class AutoMockerKeyedServicesExtensions
{
    // Generated extension methods...
}

Ambiguous Reference Issues with Multiple Test Projects

This design can cause ambiguous method call errors when multiple test projects reference each other and both have the source generators enabled. Since each project generates its own internal partial class with the same name and methods, projects that share visibility (e.g., via InternalsVisibleTo or project references) may see duplicate definitions.

Example error:

The call is ambiguous between the following methods or properties:
'Moq.AutoMock.AutoMockerKeyedServicesExtensions.WithKeyedService(...)' and
'Moq.AutoMock.AutoMockerKeyedServicesExtensions.WithKeyedService(...)'

This commonly occurs when:

• An integration test project references a unit test project
• InternalsVisibleTo is used between test projects
• Both projects reference Moq.AutoMock and the same packages that trigger generators (e.g., Microsoft.Extensions.DependencyInjection.Abstractions)

Solution: Disable the source generator in one of the projects (see Disabling Source Generators below).

For more details, see Issue #410.

Disabling Source Generators

Each source generator can be individually disabled using MSBuild properties in your project's .csproj file:

Generator	MSBuild Property
Options Extension	EnableMoqAutoMockerOptionsGenerator
Keyed Services Extension	EnableMoqAutoMockerKeyedServicesGenerator
Fake Logging Extension	EnableMoqAutoMockerFakeLoggingGenerator
Application Insights Extension	EnableMoqAutoMockerApplicationInsightsGenerator
Meter Factory Extension	EnableMoqAutoMockerMeterFactoryGenerator
Fake Time Provider Extension	EnableMoqAutoMockerFakeTimeProviderGenerator

Example: Disabling a generator

<PropertyGroup>
  <!-- Disable the Keyed Services generator -->
  <EnableMoqAutoMockerKeyedServicesGenerator>false</EnableMoqAutoMockerKeyedServicesGenerator>
</PropertyGroup>

Example: Disabling multiple generators

<PropertyGroup>
  <EnableMoqAutoMockerKeyedServicesGenerator>false</EnableMoqAutoMockerKeyedServicesGenerator>
  <EnableMoqAutoMockerOptionsGenerator>false</EnableMoqAutoMockerOptionsGenerator>
</PropertyGroup>

Tips and Best Practices

Review Generated Code

To see the generated code, enable source generators output in your .csproj:

<PropertyGroup>
  <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
  <CompilerGeneratedFilesOutputPath>$(BaseIntermediateOutputPath)Generated</CompilerGeneratedFilesOutputPath>
</PropertyGroup>