csharp-tunit

# TUnit Best Practices Your goal is to help me write effective unit tests with TUnit, covering both standard and data-driven testing approaches. ## Project Setup - Use a separate test project with naming convention `[ProjectName].Tests` - Reference TUnit package and TUnit.Assertions for fluent assertions - Create test classes that match the classes being tested (e.g., `CalculatorTests` for `Calculator`) - Use .NET SDK test commands: `dotnet test` for running tests - TUnit requires .NET 8.0 or higher ## Test Structure - No test class attributes required (like xUnit/NUnit) - Use `[Test]` attribute for test methods (not `[Fact]` like xUnit) - Follow the Arrange-Act-Assert (AAA) pattern - Name tests using the pattern `MethodName_Scenario_ExpectedBehavior` - Use lifecycle hooks: `[Before(Test)]` for setup and `[After(Test)]` for teardown - Use `[Before(Class)]` and `[After(Class)]` for shared context between tests in a class - Use `[Before(Assembly)]` and `[After(Assembly)]` for shared context across test classes - TUnit supports advanced lifecycle hooks like `[Before(TestSession)]` and `[After(TestSession)]` ## Standard Tests - Keep tests focused on a single behavior - Avoid testing multiple behaviors in one test method - Use TUnit's fluent assertion syntax with `await Assert.That()` - Include only the assertions needed to verify the test case - Make tests independent and idempotent (can run in any order) - Avoid test interdependencies (use `[DependsOn]` attribute if needed) ## Data-Driven Tests - Use `[Arguments]` attribute for inline test data (equivalent to xUnit's `[InlineData]`) - Use `[MethodData]` for method-based test data (equivalent to xUnit's `[MemberData]`) - Use `[ClassData]` for class-based test data - Create custom data sources by implementing `ITestDataSource` - Use meaningful parameter names in data-driven tests - Multiple `[Arguments]` attributes can be applied to the same test method ## Assertions - Use `await Assert.That(value).IsEqualTo(expected)` for value equality - Use `await Assert.That(value).IsSameReferenceAs(expected)` for reference equality - Use `await Assert.That(value).IsTrue()` or `await Assert.That(value).IsFalse()` for boolean conditions - Use `await Assert.That(collection).Contains(item)` or `await Assert.That(collection).DoesNotContain(item)` for collections - Use `await Assert.That(value).Matches(pattern)` for regex pattern matching - Use `await Assert.That(action).Throws<TException>()` or `await Assert.That(asyncAction).ThrowsAsync<TException>()` to test exceptions - Chain assertions with `.And` operator: `await Assert.That(value).IsNotNull().And.IsEqualTo(expected)` - Use `.Or` operator for alternative conditions: `await Assert.That(value).IsEqualTo(1).Or.IsEqualTo(2)` - Use `.Within(tolerance)` for DateTime and numeric comparisons with tolerance - All assertions are asynchronous and must be awaited ## Advanced Features - Use `[Repeat(n)]` to repeat tests multiple times - Use `[Retry(n)]` for automatic retry on failure - Use `[ParallelLimit<T>]` to control parallel execution limits - Use `[Skip("reason")]` to skip tests conditionally - Use `[DependsOn(nameof(OtherTest))]` to create test dependencies - Use `[Timeout(milliseconds)]` to set test timeouts - Create custom attributes by extending TUnit's base attributes ## Test Organization - Group tests by feature or component - Use `[Category("CategoryName")]` for test categorization - Use `[DisplayName("Custom Test Name")]` for custom test names - Consider using `TestContext` for test diagnostics and information - Use conditional attributes like custom `[WindowsOnly]` for platform-specific tests ## Performance and Parallel Execution - TUnit runs tests in parallel by default (unlike xUnit which requires explicit configuration) - Use `[NotInParallel]` to disable parallel execution for specific tests - Use `[ParallelLimit<T>]` with custom limit classes to control concurrency - Tests within the same class run sequentially by default - Use `[Repeat(n)]` with `[ParallelLimit<T>]` for load testing scenarios ## Migration from xUnit - Replace `[Fact]` with `[Test]` - Replace `[Theory]` with `[Test]` and use `[Arguments]` for data - Replace `[InlineData]` with `[Arguments]` - Replace `[MemberData]` with `[MethodData]` - Replace `Assert.Equal` with `await Assert.That(actual).IsEqualTo(expected)` - Replace `Assert.True` with `await Assert.That(condition).IsTrue()` - Replace `Assert.Throws<T>` with `await Assert.That(action).Throws<T>()` - Replace constructor/IDisposable with `[Before(Test)]`/`[After(Test)]` - Replace `IClassFixture<T>` with `[Before(Class)]`/`[After(Class)]` **Why TUnit over xUnit?** TUnit offers a modern, fast, and flexible testing experience with advanced features not present in xUnit, such as asynchronous assertions, more refined lifecycle hooks, and improved data-driven testing capabilities. TUnit's fluent assertions provide clearer and more expressive test validation, making it especially suitable for complex .NET projects.