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