XUnit Best Practices
Your goal is to help me write effective unit tests with XUnit, covering both standard and data-driven testing approaches.
Project Setup
Use a separate test project with naming convention
[ProjectName].Tests
Reference Microsoft.NET.Test.Sdk, xunit, and xunit.runner.visualstudio packages
Create test classes that match the classes being tested (e.g.,
CalculatorTests
for
Calculator
)
Use .NET SDK test commands:
dotnet test
for running tests
Test Structure
No test class attributes required (unlike MSTest/NUnit)
Use fact-based tests with
[Fact]
attribute for simple tests
Follow the Arrange-Act-Assert (AAA) pattern
Name tests using the pattern
MethodName_Scenario_ExpectedBehavior
Use constructor for setup and
IDisposable.Dispose()
for teardown
Use
IClassFixture
for shared context between tests in a class
Use
ICollectionFixture
for shared context between multiple test classes
Standard Tests
Keep tests focused on a single behavior
Avoid testing multiple behaviors in one test method
Use clear assertions that express intent
Include only the assertions needed to verify the test case
Make tests independent and idempotent (can run in any order)
Avoid test interdependencies
Data-Driven Tests
Use
[Theory]
combined with data source attributes
Use
[InlineData]
for inline test data
Use
[MemberData]
for method-based test data
Use
[ClassData]
for class-based test data
Create custom data attributes by implementing
DataAttribute
Use meaningful parameter names in data-driven tests
Assertions
Use
Assert.Equal
for value equality
Use
Assert.Same
for reference equality
Use
Assert.True
/
Assert.False
for boolean conditions
Use
Assert.Contains
/
Assert.DoesNotContain
for collections
Use
Assert.Matches
/
Assert.DoesNotMatch
for regex pattern matching
Use
Assert.Throws
or
await Assert.ThrowsAsync
to test exceptions
Use fluent assertions library for more readable assertions
Mocking and Isolation
Consider using Moq or NSubstitute alongside XUnit
Mock dependencies to isolate units under test
Use interfaces to facilitate mocking
Consider using a DI container for complex test setups
Test Organization
Group tests by feature or component
Use
[Trait("Category", "CategoryName")]
for categorization
Use collection fixtures to group tests with shared dependencies
Consider output helpers (
ITestOutputHelper
) for test diagnostics
Skip tests conditionally with
Skip = "reason"
in fact/theory attributes