nunit

# NUnit Ported from JUnit, NUnit is one of the oldest and most feature-rich frameworks for .NET. Ideally suited for complex test setups and legacy migrations. ## When to Use - **C# and .NET Testing**: A mature, feature-rich testing framework widely used across enterprise .NET applications. - **Parameterized & Combinatorial Testing**: Generating test matrices effortlessly with `[TestCase]` and `[Combinatorial]`. - **Constraint-Based Assertions**: Writing expressive assertions using the `Assert.That()` syntax. - **ASP.NET Core & Unity Game Testing**: Testing web APIs, microservices, and Unity game scripts. ## Quick Start ```csharp using NUnit.Framework; [TestFixture] public class Tests { [SetUp] public void Setup() { } [Test] public void Test1() { Assert.Pass(); } [TestCase(1, 2, 3)] [TestCase(2, 2, 4)] public void TestAdd(int a, int b, int expected) { Assert.AreEqual(expected, a + b); } } ``` ## Core Concepts ### Constraint-Based Assertion Model NUnit emphasizes fluent constraint assertions over legacy multiple-assert methods: ```csharp using NUnit.Framework; [TestFixture] public class AccountTests { [Test] public void TestDepositIncreasesBalance() { var account = new Account(100); account.Deposit(50); Assert.That(account.Balance, Is.EqualTo(150)); Assert.That(account.Transactions, Has.Count.EqualTo(1)); Assert.That(account.Owner, Does.StartWith("Jane")); } } ``` ### Parameterized Test Cases (`[TestCase]`) Passes inline parameters to test multiple input/output permutations: ```csharp [TestCase(10, 20, 30)] [TestCase(-5, 5, 0)] [TestCase(0, 0, 0)] public void Add_ReturnsCorrectSum(int a, int b, int expected) { var calculator = new Calculator(); Assert.That(calculator.Add(a, b), Is.EqualTo(expected)); } ``` ### Multiple Assertions Block (`Assert.Multiple`) Executes all assertions in a block, reporting all failures rather than terminating on the first: ```csharp [Test] public void ValidateUserRecord() { var user = GetUser(); Assert.Multiple(() => { Assert.That(user.FirstName, Is.EqualTo("Jane")); Assert.That(user.LastName, Is.EqualTo("Doe")); Assert.That(user.IsActive, Is.True); }); } ``` ## Common Patterns ### Parameterized Test Fixture with Setup **Problem**: Redundant boilerplate when testing multiple implementations of the same interface. **Solution**: Use `[TestCase]` with typed expectations: ```csharp using NUnit.Framework; [TestFixture] public class CalculatorTests { private Calculator _calculator; [SetUp] public void SetUp() { _calculator = new Calculator(); } [TestCase(5, 3, 8)] [TestCase(-1, 1, 0)] [TestCase(0, 0, 0)] public void Add_ReturnsExpectedSum(int a, int b, int expected) { int result = _calculator.Add(a, b); Assert.That(result, Is.EqualTo(expected)); } } ``` ## Best Practices **Do**: - Adopt `Assert.Multiple`: Run all field assertions on complex objects to view full failure contexts simultaneously. - Use `Assert.That` Exclusively: Modern NUnit deprecates legacy `Assert.AreEqual()` in favor of the constraint model. - Enable Parallel Execution: Add `[assembly: Parallelizable(ParallelScope.Fixtures)]` to accelerate test execution. - Pair with FluentAssertions: Combine with `FluentAssertions` library for enhanced assertion readability. **Don't**: - Use `[SetUp]` for slow integration setup: Use `[OneTimeSetUp]` for database connections shared across the fixture. - Leave static shared state unreset: Ensure parallelizable test fixtures do not mutate static state. - Write huge monolithic test methods: Keep test methods focused on single business behaviors. ## Troubleshooting | Error | Cause | Solution | | :----------------------------------------------------------------- | :--------------------------------------------------------- | :------------------------------------------------------------------------------------------- | | `No test is available in ... Make sure test project has reference` | Missing `NUnit3TestAdapter` NuGet package in test project. | Install `NUnit3TestAdapter` and `Microsoft.NET.Test.Sdk`. | | `AssertionException: Expected: ... But was: ...` | Calculation result does not match expectation. | Check logic and verify constraints using fluent `Assert.That(actual, Is.EqualTo(expected))`. | | `System.NullReferenceException in SetUp` | Accessing uninitialized fixture field in test execution. | Ensure initialization code is in a `[SetUp]` method, not in standard constructor. | ## References - [NUnit Documentation](https://nunit.org/)