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