Prompt file imported from kmaraszkiewicz86/ai-development-standards (.github/prompts/create-unit-tests.prompt.md). Copyright stays with the author.

Create Unit Tests Prompt

Create complete, production-ready unit tests for the class or feature described below, following the testing standards defined in this repository.

Instructions

Generate comprehensive unit tests following the standards in:

• .github/instructions/testing.md
• .github/instructions/naming.md

What to generate

BaseFixture (if not already present)

// Tests/Fixtures/BaseFixture.cs
namespace MyProject.Tests.Fixtures;

public abstract class BaseFixture
{
    protected IFixture AutoFixture { get; }

    protected BaseFixture()
    {
        AutoFixture = new Fixture()
            .Customize(new AutoNSubstituteCustomization { ConfigureMembers = true });
    }

    protected T Create<T>() => AutoFixture.Create<T>();
    protected IReadOnlyList<T> CreateMany<T>(int count = 3) =>
        AutoFixture.CreateMany<T>(count).ToList().AsReadOnly();
}

Feature Fixture

• One fixture per test class, inheriting BaseFixture
• Contains mocks for all external dependencies
• Constructs the system under test (SUT)
• Provides factory methods for test data

// Tests/Fixtures/CreateOrderCommandFixture.cs
namespace MyProject.Tests.Fixtures;

public sealed class CreateOrderCommandFixture : BaseFixture
{
    public IOrderRepository OrderRepository { get; }
    public IUnitOfWork UnitOfWork { get; }
    public CreateOrderCommandHandler Sut { get; }

    public CreateOrderCommandFixture()
    {
        OrderRepository = Substitute.For<IOrderRepository>();
        UnitOfWork = Substitute.For<IUnitOfWork>();
        Sut = new CreateOrderCommandHandler(OrderRepository, UnitOfWork);
    }

    public CreateOrderCommand ValidCommand() => Create<CreateOrderCommand>();

    public CreateOrderCommand CommandWithEmptyItems() =>
        new CreateOrderCommand(Guid.NewGuid(), []);
}

Test Class

Cover all of the following:

Happy Path Tests

• Expected result returned for valid input
• Correct dependencies called with expected arguments
• Correct return value / side effects

Validation Tests

• Missing required fields
• Out-of-range values
• Business rule violations

Exception Tests

• Correct exception type thrown for invalid state
• Repository failure propagated correctly
• Not-found scenarios return the correct exception

Edge Case Tests

• Empty collections
• Boundary values
• Concurrent scenarios where applicable

Test Naming Convention

Use the pattern: MethodName_Condition_ExpectedResult

// Examples
HandleAsync_WithValidCommand_CallsRepositoryAddAsync
HandleAsync_WithEmptyItems_ThrowsValidationException
HandleAsync_WhenRepositoryThrows_PropagatesException
GetByIdAsync_WithExistingId_ReturnsOrderDto
GetByIdAsync_WithUnknownId_ThrowsOrderNotFoundException

Requirements

• Use xUnit, FluentAssertions, AutoFixture, AutoNSubstitute, NSubstitute.
• Follow Arrange / Act / Assert.
• Each test verifies one behaviour.
• Use await act.Should().ThrowAsync<TException>() for exception assertions.
• Verify interactions with Received(n) — only when the interaction matters.
• No shared mutable state between tests.
• No Thread.Sleep or Task.Delay.
• No .Result or .Wait().

Class or Feature to Test

[Describe the class or feature to test here — e.g., "CreateOrderCommandHandler — a CQRS command handler that creates a new order and saves it via the repository."]