Free course

Testing JavaScript Applications

Test JavaScript from pure functions to APIs, databases, browsers, CI, and small load checks with Node.js, Testcontainers, Playwright, and k6.

5 modules · 25 lessons · No signup

Prerequisites: JavaScript, Node.js and Web APIs

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What you'll learn

Build a fast, isolated, diagnosable test strategy for the Books application across unit, integration, browser, and reliability boundaries.

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Course contents

  1. Testing foundations

    Choose evidence from risk, use the Node test runner, and make tests clear and deterministic.

    1. ✓ Choose what a test proves
    2. ✓ Run the first Node test
    3. ✓ Arrange, act, and assert
    4. ✓ Make tests deterministic
    5. ✓ Check your understanding: testing foundations

  2. Unit tests

    Test pure domain logic, boundaries, injected dependencies, and focused test doubles.

    1. ✓ Extract pure domain logic
    2. ✓ Test boundaries with tables
    3. ✓ Inject dependencies
    4. ✓ Use test doubles sparingly
    5. ✓ Check your understanding: unit tests

  3. Integration tests

    Test the HTTP stack, real schemas, migrations, SQLite, and disposable PostgreSQL.

    1. ✓ Test the HTTP contract
    2. ✓ Isolate database tests
    3. ✓ Test migrations and constraints
    4. ✓ Use Testcontainers for PostgreSQL
    5. ✓ Check your understanding: integration tests

  4. Browser tests

    Exercise user journeys with Playwright locators, web-first assertions, and traces.

    1. ✓ Install Playwright
    2. ✓ Locate elements by role
    3. ✓ Wait for observable state
    4. ✓ Debug with traces
    5. ✓ Check your understanding: browser tests

  5. Reliability and CI

    Use coverage, CI stages, k6 thresholds, and a maintainable test ownership model.

    1. ✓ Use coverage as a map
    2. ✓ Build a CI test pipeline
    3. ✓ Add a k6 smoke test
    4. ✓ Finish the testing strategy
    5. ✓ Check your understanding: reliability and ci