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csharp-nunit

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

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NUnit Best Practices

Your goal is to help me write effective unit tests with NUnit, 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, NUnit, and NUnit3TestAdapter 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

  • Apply [TestFixture] attribute to test classes
  • Use [Test] attribute for test methods
  • Follow the Arrange-Act-Assert (AAA) pattern
  • Name tests using the pattern MethodName_Scenario_ExpectedBehavior
  • Use [SetUp] and [TearDown] for per-test setup and teardown
  • Use [OneTimeSetUp] and [OneTimeTearDown] for per-class setup and teardown
  • Use [SetUpFixture] for assembly-level setup and teardown

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 [TestCase] for inline test data
  • Use [TestCaseSource] for programmatically generated test data
  • Use [Values] for simple parameter combinations
  • Use [ValueSource] for property or method-based data sources
  • Use [Random] for random numeric test values
  • Use [Range] for sequential numeric test values
  • Use [Combinatorial] or [Pairwise] for combining multiple parameters

Assertions

  • Use Assert.That with constraint model (preferred NUnit style)
  • Use constraints like Is.EqualTo, Is.SameAs, Contains.Item
  • Use Assert.AreEqual for simple value equality (classic style)
  • Use CollectionAssert for collection comparisons
  • Use StringAssert for string-specific assertions
  • Use Assert.Throws<T> or Assert.ThrowsAsync<T> to test exceptions
  • Use descriptive messages in assertions for clarity on failure

Mocking and Isolation

  • Consider using Moq or NSubstitute alongside NUnit
  • 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 categories with [Category("CategoryName")]
  • Use [Order] to control test execution order when necessary
  • Use [Author("DeveloperName")] to indicate ownership
  • Use [Description] to provide additional test information
  • Consider [Explicit] for tests that shouldn't run automatically
  • Use [Ignore("Reason")] to temporarily skip tests