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
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)
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.
