.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, orAcceptance [TestCategory("Integration")](MSTest)[Trait("Category", "Integration")](xUnit)[Category("Integration")](NUnit)- Project name ending in
.IntegrationTestsor.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 |