/csharp-nunit

name: csharp-nunit
description: 'Get best practices for NUnit unit testing, including data-driven tests'

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