Visitor Check Question Explained
This worked Harness Engineering practice question tests Checks and Sensors. Try the answer first, then review why B is the best choice.
Short answer
The correct answer is B. A visitor check: click the link yourself and record the result.
A script tests only what it was written to test. This one confirmed that an element with id="menu" existed, not that the element was the menu. Some problems are easiest to find by opening the page and using it. A short list of visitor checks, each recorded as pass, fail, or not checked, covers what the script does not test, such as where a link lands and how the page looks at phone width. The correct answer is B. A visitor check: click the link yourself and record the result
The Question
Your link checker passes. But when you click "View menu" on the live page, it jumps to the footer, because the id="menu" attribute sits on the wrong element. What was missing?
Why B is correct
A script tests only what it was written to test. This one confirmed that an element with id="menu" existed, not that the element was the menu. Some problems are easiest to find by opening the page and using it. A short list of visitor checks, each recorded as pass, fail, or not checked, covers what the script does not test, such as where a link lands and how the page looks at phone width. The correct answer is B. A visitor check: click the link yourself and record the result
Why the other options are wrong
The script was correct about what it tested. Running it again returns the same pass, because the id does exist on the page.
A rule in AGENTS.md may stop the next mistake, but it does not find this one. You need a check that reports the problem on the current page.
A description is the agent's intent, not the page's behavior. The link already did something other than what the agent intended.
Key idea: Checks and Sensors
Every question here is a situation you meet with Claude Code or Codex: the agent gets something wrong, and you choose what to change. The best answer is usually a file, a check, or a hook that stops the mistake from repeating, not a louder prompt. If you miss a question, read the explanation and note which part of the harness it uses: the AGENTS.md map, a skill, a check, a visitor check, a hook, or a handoff note.
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