bi-13 step 03 — The break-and-observe loop

Goal

Prove you have connected spec → test → implementation by deliberately breaking the chain.

Tasks

1. Pick a behaviour you understand well.
2. Read the spec text that defines it.
3. Locate the WPT that tests it.
4. Run the test; confirm it passes.
5. Break the Blink implementation deliberately. Observe the exact failure.
6. Restore. Confirm green.
7. Write a testharness.js test for the parsing lab's Case B. Run it against unpatched Chromium first — a test that passes before your change is not a test.
8. Reason about whether your test should pass in other engines, and why.

Done when

• Full loop completed with the failure observed
• A new testharness.js test written, verified to fail when the behaviour is wrong
• You can name the layer any given bug should be tested at, and defend it