Csharp Nunit

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