.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