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Claude/ChatGPT Prompt to Build a Prompt-Injection Test Suite

Prompt-injection test suite for an LLM feature: 15 adversarial inputs, expected safe behaviour, an automated scoring harness, and a mitigation checklist.

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Edit the values, then copy your finished prompt.

Jouw Prompt
prompt.txt

                                

What this prompt does

This prompt builds a prompt-injection test suite for an LLM feature and returns runnable harness code plus real adversarial inputs, not descriptions of them. It generates 15 attack cases spanning direct injection, indirect injection (malicious instructions hidden in tool output or document content), role flips, jailbreaks, and data exfiltration, each paired with the expected safe behavior. It then writes an automated harness that scores pass/fail with a rubric sensitive to partial leaks.

The variables target the suite at your system. [feature] describes what is under test — an email assistant that reads an inbox has a very different indirect-injection surface than a document summarizer. [llm_model] is the model the feature uses, so the cases and expectations fit its behavior. [lang] sets the harness language so the scoring code drops into your test setup. The prompt deliberately insists on indirect cases because injection that rides in on data, not the user's message, is the one teams skip.

When to use it

  • Your LLM feature reads untrusted content: inboxes, uploaded docs, tool output
  • You want explicit indirect-injection coverage, not just direct prompt attacks
  • You need a runnable harness that scores the suite, not a list of ideas
  • You want a rubric that flags partial leaks, not only outright failures
  • You are gating releases and need the highest-risk inputs identified
  • You want to re-run injection tests on every prompt change to catch regressions

Example output

The model returns 15 adversarial test inputs grouped by attack type with their expected safe behavior, then an automated harness in your chosen language that runs the suite and scores each case pass or fail. It includes a scoring rubric that catches partial leaks, a mitigation checklist (structured tool schemas, input scrubbing, output validation, monitoring), and a shortlist of the three highest-risk inputs to gate releases on.

Pro tips

  • Describe [feature] with its real data sources ("reads the user's inbox and calendar") so the indirect cases match your actual attack surface
  • Set [llm_model] to the model you ship; expected safe behavior depends on how that model handles refusals and tool calls
  • Choose [lang] to match your existing test runner so the harness integrates rather than living off to the side
  • Lean into the indirect-injection cases — instructions hidden in documents or tool output are the quiet killer that direct tests miss
  • Use the partial-leak rubric; a case that leaks half a secret should not score as a pass
  • Re-run the suite on every prompt or tool-schema change, because injection defenses regress silently and without warning
  • Wire the harness into CI so the three highest-risk inputs gate releases automatically rather than relying on someone remembering to run it

Frequently Asked Questions

Does the suite cover indirect injection, not just direct attacks?
Yes, and it emphasizes them. The prompt requires indirect cases where the malicious instruction rides in on tool or document content rather than the user's message. Those are the attacks teams most often skip, so the prompt builds them explicitly.
Do I get actual runnable test code or just a description?
You get runnable harness code in the language you set in `[lang]`, along with the 15 real adversarial inputs. The harness runs the suite and scores each case, so you can drop it into your test setup rather than translating a description into code yourself.
How does the scoring handle a partial information leak?
The rubric is designed to flag partial leaks, not only outright failures. A response that leaks half a secret or partially follows an injected instruction is caught rather than passing, which is important because partial compromises are easy to miss with a naive pass/fail check.
How often should I run this suite?
Re-run it on every prompt change and tool-schema change. Injection defenses regress silently, so a tweak that looks harmless can reopen an attack path. Gating releases on the three highest-risk inputs the prompt identifies gives you a fast safety check each time.
Engr Mejba Ahmed

Need this built for real?

Engr Mejba Ahmed

AI Developer · Software Engineer

I'm Mejba — I design and ship production AI systems, automations, and full-stack apps. If you want this turned into a working solution for your team, let's talk.

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Engr Mejba Ahmed

Engr Mejba Ahmed

Claude Code Expert · Online

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