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name: csharp-test description: > Testing standards for C# 14 / .NET 10 with xUnit and Shouldly. Covers naming conventions (Should_X_When_Y), AAA pattern, test data builders, and mocking rules. Use for writing tests, "/test", or "help with tests". user-invocable: true allowed-tools:

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• Glob metadata: author: csharp-standards version: "4.0.0"

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Testing Standards

Write tests that are readable, maintainable, and reliable.

Core Principles

Quick Rules

1. NO logic in tests — zero if, for, while
2. ONE act per test — single method call
3. NO Thread.Sleep — use TimeProvider
4. NO mocking records/structs — use real instances
5. FluentAssertions FORBIDDEN — use Shouldly

Test Structure Template

Copypublic sealed class OrderServiceTests {
    [Fact]
    public async Task Should_CreateOrder_When_ValidInput() {
        // Arrange
        var repository = Substitute.For<IOrderRepository>();
        var sut = new OrderService(repository);
        var command = new CreateOrderCommand(CustomerId.New(), Money.FromDecimal(99.99m));

        // Act
        var result = await sut.CreateAsync(command, CancellationToken.None);

        // Assert
        result.IsError.ShouldBeFalse();
        result.Value.Id.ShouldNotBe(OrderId.Empty);
    }
}

Testing Internal Types

Add to main project .csproj:

Copy<ItemGroup>
  <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
    <_Parameter1>MyProduct.Tests</_Parameter1>
  </AssemblyAttribute>
</ItemGroup>

Code Coverage

Copydotnet test --collect:"XPlat Code Coverage"

Required package in test project:

Copy<PackageReference Include="coverlet.collector" />

References

Load detailed documentation as needed: