Unit Testing Fundamentals

Jest Setup and Test Structure with describe, it, and expect

Master Jest's core API: describe blocks, it/test functions, expect assertions, and beforeEach/afterEach lifecycle hooks for writing well-organised, maintainable test suites.

AAA Pattern, Test Naming, and File Organisation

Learn the Arrange-Act-Assert pattern, write test names that produce self-documenting failure messages, and organise test files alongside source for maximum cohesion.

45 min

Testing Asynchronous Code with async/await, resolves, and rejects

Test Promises, async/await functions, and rejected errors correctly in Jest, avoiding the silent false-positive trap where forgotten awaits let failing tests appear green.

Mocking with jest.fn, jest.spyOn, and Module Mocks

Master Jest's mocking system: create mock functions with jest.fn(), wrap real methods with jest.spyOn(), mock entire modules with jest.mock(), and verify call arguments precisely.

Code Coverage Analysis with Istanbul and Jest

Measure and interpret statement, branch, function, and line coverage metrics, configure coverage thresholds, and generate HTML reports to identify untested code paths.

Testing React Components with React Testing Library

Test React components from the user's perspective using React Testing Library: render, query by role and text, fire events, and assert on visible output without testing implementation details.

Testing Angular Components and Services with TestBed

Use Angular's TestBed to configure testing modules, test components with ComponentFixture, mock services with jasmine spies, and test Angular forms and HTTP calls.

Testing Vue Components with Vue Test Utils and Vitest

Test Vue 3 components using Vue Test Utils and Vitest: mount components, simulate user events, test Composition API logic, mock Pinia stores, and test async component behaviour.

Unit Testing Best Practices and Common Anti-Patterns

Master professional unit testing discipline: eliminate brittle tests, detect and fix test interdependence, avoid over-mocking, and maintain a test suite as a first-class engineering asset.