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