Agent skill
testing-xunit
Use when writing unit tests, integration tests, or setting up test projects in C#. Covers xUnit patterns, Moq mocking, Bogus test data generation, and Alba integration testing.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/testing-xunit
SKILL.md
xUnit Testing
Apply these patterns when writing tests in .NET projects.
Required Packages
<PackageReference Include="xunit" Version="2.*" />
<PackageReference Include="xunit.runner.visualstudio" Version="2.*" />
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.*" />
<PackageReference Include="Moq" Version="4.*" />
<PackageReference Include="Bogus" Version="35.*" />
<PackageReference Include="Alba" Version="8.*" /> <!-- Integration tests -->
Project Structure
tests/
├── MyApp.UnitTests/
│ ├── GlobalUsings.cs
│ ├── Fakers/UserFaker.cs
│ └── Services/UserServiceTests.cs
└── MyApp.IntegrationTests/
└── Endpoints/UserEndpointsTests.cs
GlobalUsings.cs:
global using Xunit;
global using Moq;
global using Bogus;
Test Naming
Pattern: MethodName_Scenario_ExpectedResult
GetByIdAsync_WithValidId_ReturnsUser()
GetByIdAsync_WithInvalidId_ReturnsNull()
CreateAsync_WithDuplicateEmail_ThrowsValidationException()
Test Structure
[Fact]
public async Task GetByIdAsync_WithValidId_ReturnsUser()
{
// Arrange
var expectedUser = new UserFaker().Generate();
_mockRepo.Setup(r => r.GetByIdAsync(expectedUser.Id)).ReturnsAsync(expectedUser);
// Act
var result = await _sut.GetByIdAsync(expectedUser.Id);
// Assert
Assert.NotNull(result);
Assert.Equal(expectedUser.Name, result.Name);
}
Test Data with Bogus
public sealed class UserFaker : Faker<User>
{
public UserFaker()
{
RuleFor(u => u.Id, f => f.IndexFaker + 1);
RuleFor(u => u.Email, f => f.Internet.Email());
RuleFor(u => u.FirstName, f => f.Name.FirstName());
RuleFor(u => u.IsActive, true);
}
public UserFaker AsInactive()
{
RuleFor(u => u.IsActive, false);
return this;
}
}
var user = new UserFaker().Generate();
var users = new UserFaker().Generate(10);
var inactiveUser = new UserFaker().AsInactive().Generate();
Mocking with Moq
public class UserServiceTests
{
private readonly Mock<IUserRepository> _mockRepo;
private readonly UserService _sut;
public UserServiceTests()
{
_mockRepo = new Mock<IUserRepository>();
_sut = new UserService(_mockRepo.Object);
}
}
// Setup
_mockRepo.Setup(r => r.GetByIdAsync(1)).ReturnsAsync(new User { Id = 1 });
_mockRepo.Setup(r => r.GetByIdAsync(It.IsAny<int>())).ReturnsAsync(new User());
_mockRepo.Setup(r => r.GetByIdAsync(-1)).ThrowsAsync(new ArgumentException());
// Verify
_mockRepo.Verify(r => r.GetByIdAsync(1), Times.Once);
_mockRepo.Verify(r => r.DeleteAsync(It.IsAny<int>()), Times.Never);
Integration Testing with Alba
public class UserEndpointsTests : IAsyncLifetime
{
private IAlbaHost _host = null!;
public async Task InitializeAsync()
{
_host = await AlbaHost.For<Program>(builder =>
{
builder.ConfigureServices(services =>
{
services.AddSingleton<IUserRepository, FakeUserRepository>();
});
});
}
public async Task DisposeAsync() => await _host.DisposeAsync();
[Fact]
public async Task GetUser_WithValidId_ReturnsOk()
{
await _host.Scenario(_ =>
{
_.Get.Url("/api/users/1");
_.StatusCodeShouldBeOk();
});
}
[Fact]
public async Task CreateUser_WithValidData_ReturnsCreated()
{
var newUser = new UserFaker().Generate();
var result = await _host.Scenario(_ =>
{
_.Post.Json(newUser).ToUrl("/api/users");
_.StatusCodeShouldBe(HttpStatusCode.Created);
});
var created = await result.ReadAsJsonAsync<User>();
Assert.Equal(newUser.Email, created.Email);
}
}
Shared Host with Collection Fixture
public class AppFixture : IAsyncLifetime
{
public IAlbaHost Host { get; private set; } = null!;
public async Task InitializeAsync() => Host = await AlbaHost.For<Program>();
public async Task DisposeAsync() => await Host.DisposeAsync();
}
[CollectionDefinition("App")]
public class AppCollection : ICollectionFixture<AppFixture> { }
[Collection("App")]
public class UserEndpointsTests
{
private readonly IAlbaHost _host;
public UserEndpointsTests(AppFixture fixture) => _host = fixture.Host;
}
Test Attributes
[Fact] // Single test case
[Theory] // Parameterized
[InlineData(2, 3, 5)]
[InlineData(0, 0, 0)]
public void Add_TwoNumbers_ReturnsSum(int a, int b, int expected)
{
Assert.Equal(expected, Calculator.Add(a, b));
}
[Theory]
[MemberData(nameof(GetTestCases))]
public void Process_WithTestCases_ReturnsExpected(User input, bool expected) { }
[Trait("Category", "Unit")] // Run with: dotnet test --filter "Category=Unit"
Assertions
Assert.Equal(expected, actual);
Assert.NotNull(obj);
Assert.True(condition);
Assert.Empty(collection);
Assert.Contains(item, collection);
Assert.Single(collection);
Assert.Throws<ArgumentException>(() => DoSomething());
await Assert.ThrowsAsync<InvalidOperationException>(() => DoSomethingAsync());
Assert.IsType<User>(result);
Requirements
- One assertion focus per test
- Use
MethodName_Scenario_Expectednaming - Keep tests independent with no shared mutable state
- Use Bogus for realistic test data
- Mock external dependencies only
- Test edge cases: null, empty, boundaries
- Use Theory for data variations
- Use Alba for integration tests
Do not test implementation details. Do not mock the system under test. Do not use Thread.Sleep. Do not share mutable test data.
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