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csharp-xunit

✓ Official★ 36,202

by github · part of github/awesome-copilot

Get best practices for XUnit unit testing, including data-driven tests

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🧩 One of 7 skills in the github/awesome-copilot package — works on its own, and pairs well with its siblings.

This is the playbook your agent receives when the skill activates — you don't need to read it to use the skill, but it's here to audit before installing.

XUnit Best Practices

Your goal is to help me write effective unit tests with XUnit, covering both standard and data-driven testing approaches.

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<T> for shared context between tests in a class
  • Use ICollectionFixture<T> 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<T> or await Assert.ThrowsAsync<T> 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