The short version
- Refactoring should preserve behavior. These prompts require existing tests, a focused change and a diff that can be reviewed before any cleanup is accepted.
- Never paste credentials, private customer data or entire proprietary repositories into an unapproved assistant. Run suggested commands and tests in your own environment. A plausible patch is not evidence that the change works.
Refactoring should preserve behavior. These prompts require existing tests, a focused change and a diff that can be reviewed before any cleanup is accepted.
Never paste credentials, private customer data or entire proprietary repositories into an unapproved assistant. Run suggested commands and tests in your own environment. A plausible patch is not evidence that the change works.
How to use this collection
Pick the task closest to your work. Copy the prompt, replace the generic scene or code context with your own facts, and keep the constraints that help you judge the result. Change one variable at a time so you can tell what improved.
The approach follows the GitHub Copilot prompt engineering guide: provide concrete context and inspect the output rather than assuming a polished first pass is correct.
Diagnose prompts
This set focuses on diagnose. Supply your real code and test command before accepting the answer.
1. A long conditional chain
Help with a long conditional chain in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
2. A duplicated validation rule
Help with a duplicated validation rule in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
3. A database helper with side effects
Help with a database helper with side effects in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
4. A large React component
Help with a large React component in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
5. A tangled API controller
Help with a tangled API controller in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
6. A magic-string configuration
Help with a magic-string configuration in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
7. A utility with vague names
Help with a utility with vague names in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
8. A slow loop
Help with a slow loop in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
9. A legacy callback chain
Help with a legacy callback chain in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
10. A scattered permission check
Help with a scattered permission check in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then state competing hypotheses, request a minimal reproduction and identify evidence that separates them. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the proposed reproduction before applying a patch.
Implement prompts
This set focuses on implement. Supply your real code and test command before accepting the answer.
11. A long conditional chain
Help with a long conditional chain in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
12. A duplicated validation rule
Help with a duplicated validation rule in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
13. A database helper with side effects
Help with a database helper with side effects in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
14. A large React component
Help with a large React component in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
15. A tangled API controller
Help with a tangled API controller in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
16. A magic-string configuration
Help with a magic-string configuration in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
17. A utility with vague names
Help with a utility with vague names in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
18. A slow loop
Help with a slow loop in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
19. A legacy callback chain
Help with a legacy callback chain in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
20. A scattered permission check
Help with a scattered permission check in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then make the smallest change that satisfies the stated behavior and show a focused diff. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Review the diff for unrelated changes and unintended data access.
Test boundaries prompts
This set focuses on test boundaries. Supply your real code and test command before accepting the answer.
21. A long conditional chain
Help with a long conditional chain in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then add unit or integration cases for empty, invalid and concurrent inputs as appropriate. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the tests and check that they fail before the fix when feasible.
22. A duplicated validation rule
Help with a duplicated validation rule in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then add unit or integration cases for empty, invalid and concurrent inputs as appropriate. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the tests and check that they fail before the fix when feasible.
23. A database helper with side effects
Help with a database helper with side effects in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then add unit or integration cases for empty, invalid and concurrent inputs as appropriate. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the tests and check that they fail before the fix when feasible.
24. A large React component
Help with a large React component in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then add unit or integration cases for empty, invalid and concurrent inputs as appropriate. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the tests and check that they fail before the fix when feasible.
25. A tangled API controller
Help with a tangled API controller in my existing codebase. Ask for the relevant file, expected behavior, actual behavior and test command if I have not supplied them. Then add unit or integration cases for empty, invalid and concurrent inputs as appropriate. Preserve public interfaces unless evidence requires a change. Show assumptions, a focused diff and the exact command I should run. Do not invent files, test results or security guarantees.Review: Run the tests and check that they fail before the fix when feasible.
What to check before you use the result
Never paste credentials, private customer data or entire proprietary repositories into an unapproved assistant. Run suggested commands and tests in your own environment. A plausible patch is not evidence that the change works.
If the output misses the task, shorten the prompt and specify the missing fact or constraint. Keep a record of the version you used so the final asset or code change can be reproduced.
Further reading
Continue with a related guide
Put it into practice
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