microsoft/dotnet-test-frameworks

.NET Test Framework Reference

Language-specific detection patterns for .NET test frameworks (MSTest, xUnit, NUnit, TUnit).

Test File Identification

| Framework | Test class markers | Test method markers | | --------- | ------------------ | ------------------- | | MSTest | [TestClass] | [TestMethod], [DataTestMethod] | | xUnit | (none — convention-based) | [Fact], [Theory] | | NUnit | [TestFixture] | [Test], [TestCase], [TestCaseSource] | | TUnit | [ClassDataSource] | [Test] |

Assertion APIs by Framework

| Category | MSTest | xUnit | NUnit | | -------- | ------ | ----- | ----- | | Equality | Assert.AreEqual | Assert.Equal | Assert.That(x, Is.EqualTo(y)) | | Boolean | Assert.IsTrue / Assert.IsFalse | Assert.True / Assert.False | Assert.That(x, Is.True) | | Null | Assert.IsNull / Assert.IsNotNull | Assert.Null / Assert.NotNull | Assert.That(x, Is.Null) | | Exception | Assert.Throws<T>() / Assert.ThrowsExactly<T>() | Assert.Throws<T>() | Assert.That(() => ..., Throws.TypeOf<T>()) | | Collection | CollectionAssert.Contains | Assert.Contains | Assert.That(col, Has.Member(x)) | | String | StringAssert.Contains | Assert.Contains(str, sub) | Assert.That(str, Does.Contain(sub)) | | Type | Assert.IsInstanceOfType | Assert.IsAssignableFrom | Assert.That(x, Is.InstanceOf<T>()) | | Inconclusive | Assert.Inconclusive() | skip via [Fact(Skip)] | Assert.Inconclusive() | | Fail | Assert.Fail() | Assert.Fail() (.NET 10+) | Assert.Fail() |

Third-party assertion libraries: Should* (Shouldly), .Should() (FluentAssertions / AwesomeAssertions), Verify() (Verify).

Sleep/Delay Patterns

| Pattern | Example | | ------- | ------- | | Thread sleep | Thread.Sleep(2000) | | Task delay | await Task.Delay(1000) | | SpinWait | SpinWait.SpinUntil(() => condition, timeout) |

Skip/Ignore Annotations

| Framework | Annotation | With reason | | --------- | ---------- | ----------- | | MSTest | [Ignore] | [Ignore("reason")] | | xUnit | [Fact(Skip = "reason")] | (reason is required) | | NUnit | [Ignore("reason")] | (reason is required) | | TUnit | [Skip("reason")] | (reason is required) | | Conditional | #if false / #if NEVER | (no reason possible) |

Exception Handling — Idiomatic Alternatives

When a test uses try/catch to verify exceptions, suggest the framework-native alternative:

MSTest:

// Instead of try/catch (matches exact type):
var ex = Assert.ThrowsExactly<InvalidOperationException>(
    () => processor.ProcessOrder(emptyOrder));
Assert.AreEqual("Order must contain at least one item", ex.Message);

// Or (also matches derived types):
var ex = Assert.Throws<InvalidOperationException>(
    () => processor.ProcessOrder(emptyOrder));
Assert.AreEqual("Order must contain at least one item", ex.Message);

xUnit:

var ex = Assert.Throws<InvalidOperationException>(
    () => processor.ProcessOrder(emptyOrder));
Assert.Equal("Order must contain at least one item", ex.Message);

NUnit:

var ex = Assert.Throws<InvalidOperationException>(
    () => processor.ProcessOrder(emptyOrder));
Assert.That(ex.Message, Is.EqualTo("Order must contain at least one item"));

Mystery Guest — Common .NET Patterns

| Smell indicator | What to look for | | --------------- | ---------------- | | File system | File.ReadAllText, File.Exists, File.WriteAllBytes, Directory.GetFiles, Path.Combine with hard-coded paths | | Database | SqlConnection, DbContext (without in-memory provider), SqlCommand | | Network | HttpClient without HttpMessageHandler override, WebRequest, TcpClient | | Environment | Environment.GetEnvironmentVariable, Environment.CurrentDirectory | | Acceptable | MemoryStream, StringReader, InMemory database providers, custom DelegatingHandler |

Integration Test Markers

Recognize these as integration tests (adjust smell severity accordingly):

• Class name contains Integration, E2E, EndToEnd, or Acceptance
• [TestCategory("Integration")] (MSTest)
• [Trait("Category", "Integration")] (xUnit)
• [Category("Integration")] (NUnit)
• Project name ending in .IntegrationTests or .E2ETests

Setup/Teardown Methods

| Framework | Setup | Teardown | | --------- | ----- | -------- | | MSTest | [TestInitialize] or constructor | [TestCleanup] or IDisposable.Dispose / IAsyncDisposable.DisposeAsync | | xUnit | constructor | IDisposable.Dispose / IAsyncDisposable.DisposeAsync | | NUnit | [SetUp] | [TearDown] | | MSTest (class) | [ClassInitialize] | [ClassCleanup] | | NUnit (class) | [OneTimeSetUp] | [OneTimeTearDown] | | xUnit (class) | IClassFixture<T> | fixture's Dispose |