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Web Development · module 12 of 13

Testing & Debugging

Debug systematically, isolate pure logic, write focused tests, inspect browser tools, and protect important behavior from regressions.

Course map
end-to-endintegrationunitslow, brittleclosest to real usefast, focusedrun on every saveThe shape is a budget,not a rule. A fewend-to-end tests provethe app works; manyunit tests tell youexactly what broke.
Testing & Debugging — the idea in one picture

What this module covers

5 steps · Web Development

  1. Step 1. Lesson: Testing & Debugging

    Debug systematically, isolate pure logic, write focused tests, inspect browser tools, and protect important behavior from regressions. Learning objectives - Recognize when testing & debugging is the right tool. - Explain the role of test, expect, console. - Build a small working example before combining it with a larger interface. - Identify one accessibility, maintainability, or error-handling improvement. Read the example, predict what it will do, then complete the small change described in the check question.

    Debug systematically, isolate pure logic, write focused tests, inspect browser tools, and protect important behavior from regressions. In Web Lab, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [Web Lab] Use the example to demonstrate testing & debugging.

  2. Step 2. Quiz: Testing & Debugging

    Check your understanding of Testing & Debugging.

    A repeatable reproduction gives you evidence and confirms whether the eventual fix works. In Web Lab, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [Web Lab] Complete the knowledge check.

  3. Step 3. Exercise: Testing & Debugging

    Diagnose a broken total calculator, reproduce the bug, isolate the failing function, and add tests for normal and edge cases.

    This exercise turns the Testing & Debugging lesson into a working code change. In Web Lab, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [Web Lab] Does the solution use test and expect and console?

  4. Step 4. Review lab: Explain & improve Testing & Debugging

    Rebuild the exercise without copying the solution. Then improve it in two ways: make the code easier to understand and add one useful edge case, responsive behavior, accessibility improvement, or error state. Finally, write a short explanation of how test, expect, console work together.

    Rebuilding from memory and improving an edge case turns recognition into durable skill. In Web Lab, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [Web Lab] Does the improved version still use test, expect, console clearly?

  5. Step 5. Mini project: Testing & Debugging

    Add a practical test and debugging plan to a data-driven app, covering validation, rendering, failed requests, and persisted state.

    The mini project combines the module lesson, quiz, and exercise into one portfolio-ready result. In Web Lab, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [Web Lab] Does the project apply the module's testing & debugging skills?

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