backend-testing - SKILL.md Agent Skill

name: backend-testing description: > Use this skill when writing or modifying C# tests — unit tests, integration tests, or test fixtures. Covers xUnit patterns, AppWebHostFactory for integration testing, FluentClient for API assertions, ProxyTimeProvider for time manipulation, and test data builders. Apply when adding new test cases, debugging test failures, or setting up test infrastructure.

Backend Testing

Test Naming Standards

Pattern: MethodUnderTest_Scenario_ExpectedBehavior

MethodUnderTest — The actual method on the class being tested, not necessarily the entry point you call.
Scenario — The input, state, or condition being tested.
ExpectedBehavior — What the method should do or return.

// ✅ Good
[Fact]
public void GetValue_JObjectWithUserInfo_ReturnsTypedUserInfo() { }
[Fact]
public async Task PostEvent_WithValidPayload_ReturnsAccepted() { }

// ❌ Bad: Vague or wrong method name
[Fact]
public void TestGetValue() { }
[Fact]
public void Deserialize_EmptyArray_ReturnsEmptyList() { }  // Wrong: name the method under test, not the entry point

Test Folder Structure

tests/Exceptionless.Tests/
├── AppWebHostFactory.cs         # WebApplicationFactory for integration tests
├── IntegrationTestsBase.cs      # Base class for integration tests
├── TestWithServices.cs          # Base class for unit tests with DI
├── Controllers/                 # API controller tests
├── Jobs/                        # Job tests
├── Repositories/                # Repository tests
├── Services/                    # Service tests
├── Utility/                     # Test data builders
│   ├── AppSendBuilder.cs        # Fluent HTTP request builder
│   ├── DataBuilder.cs           # Test data creation
│   ├── ProxyTimeProvider.cs     # Time manipulation
│   └── ...
└── Validation/                  # Validator tests

Integration Test Base

Inherit from IntegrationTestsBase (extends Foundatio.Xunit's TestWithLoggingBase):

public abstract class IntegrationTestsBase : TestWithLoggingBase, IAsyncLifetime, IClassFixture<AppWebHostFactory>

Key members: GetService<T>(), CreateFluentClient(), SendRequestAsync(), RefreshDataAsync(), ResetDataAsync(), TimeProvider (ProxyTimeProvider).

HTTP Test Pattern

Use SendRequestAsync with AppSendBuilder for HTTP testing:

await SendRequestAsync(r => r
    .Post()
    .AsTestOrganizationUser()
    .AppendPath("organizations")
    .Content(new NewOrganization { Name = "Test" })
    .StatusCodeShouldBeCreated()
);

Auth helpers: AsGlobalAdminUser(), AsTestOrganizationUser(), AsFreeOrganizationUser(), AsTestOrganizationClientUser() (API key bearer token).

Test Data Builders

var (stacks, events) = await CreateDataAsync(b => b
    .Event()
    .TestProject()
    .Type(Event.KnownTypes.Error)
    .Message("Test error"));

ProxyTimeProvider

NOT ISystemClock — use .NET 8+ TimeProvider with ProxyTimeProvider:

TimeProvider.Advance(TimeSpan.FromHours(1));
TimeProvider.SetUtcNow(new DateTimeOffset(2024, 1, 15, 12, 0, 0, TimeSpan.Zero));
TimeProvider.Restore();

Test Principles

Regression coverage — Add a focused failing test first when a bug fix can be reproduced cheaply
Use real serializer — Tests use the same JSON serializer as production
Refresh after writes — Call RefreshDataAsync() after database changes
Clean state — ResetDataAsync() clears data between integration tests