testing-basics

The AAA pattern—Arrange, Act, Assert—structures unit tests into three phases: set up test data and mocks (Arrange), execute the code being tested (Act), and verify the results match expectations (Assert). This standardized approach makes tests readable and maintainable across any language or framework.

Install a testing framework for your language, create test files alongside your code, and write tests using the AAA pattern. Name tests clearly to describe what they verify, isolate the code under test using mocks for external dependencies, and run tests before committing to catch regressions early.

Unit tests verify individual functions in isolation; integration tests check that components work together; end-to-end tests validate entire workflows from user input to final output. Each type catches different categories of bugs—unit tests find logic errors, integration tests expose component interactions, and E2E tests verify system behavior.

Create mock objects that simulate the behavior of external services, databases, or APIs without calling them directly. Inject mocks into the code being tested, specify their expected return values, and verify they were called correctly. This isolates your tests and makes them fast and reliable.

Aim for coverage that protects critical business logic and error paths—typically 70–80% for most projects—rather than chasing 100%. Focus on meaningful coverage: test edge cases, error handling, and integration points. A quick pre-commit checklist helps ensure tests run and key scenarios are covered before pushing code.

Yes. Core testing patterns like AAA, test naming conventions, isolation, and mocking principles apply universally across languages and frameworks. Each language has its own testing tools, but the underlying structure and reasoning remain consistent.