Two testing skills · both proven

differential-review vs grilling

Both skills were run through Claude twice: once on a fixed brief without the skill, once with it. The briefs differ because each is written for the job the skill claims to do, so compare each skill against its own baseline, then decide which difference matters for your work.

differential-review

Performs security-focused differential review of code changes. Adapts analysis depth to codebase size, uses git blame for context, calculates blast radius by counting callers, checks test coverage of modified code, and generates a markdown report. Use when reviewing a PR, commit, or diff for security vulnerabilities, checking whether a change re-introduces a previously fixed bug, asking what else…

Category: Testing
Source: trailofbits/skills
License: Other
Proof model: claude-opus-5-5
Brief: “Do a security-focused review of this change and present it as a single HTML page. Commit: "Allow admins to impersonate users for support" +app.get('/admin/impersonate/:id', async (req, res) => { + if (req.cookies.role !== 'admin') return res.sendStatus(403); + const user = await User.findById(req.params.id); + req.session.userId = user.id; + res.redirect(req.query.next || '/'); +});”
Skill commit: 2be6433

Without the skillWith differential-review

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Without, runWith differential-review, run3 independent runs per side, none selected by hand.

Download the with-skill page

grilling

Grill the user relentlessly about a plan, decision, or idea. Use when the user wants to stress-test their thinking, or uses any 'grill' trigger phrases.

Category: Testing
Source: mattpocock/skills
License: MIT
Proof model: claude-opus-5-5
Brief: “Here is my plan. I want to launch a paid newsletter for independent game developers in six weeks. It will cost $8 a month, come out every Tuesday, and cover marketing tips, funding opportunities and interviews with developers who shipped on Steam. I have 1,200 followers on X and no email list yet. My goal is 500 paying subscribers in the first year. Grill me on this plan, and present the result as a single HTML page: every question you would ask me, in the order you would ask it, why each one matters, and what a weak answer would tell you.”
Skill commit: 5beb35b

Without the skillWith grilling

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Without, runWith grilling, run3 independent runs per side, none selected by hand.

Download the with-skill page

We don’t pick a winner for you: the pages are the evidence. Both proofs can be repeated with the brief, model and commit shown above. See alternatives to differential-review or alternatives to grilling.