Test Backfiller
Test coverage backfill
Finds the code paths your suite never touches and writes tests that would genuinely catch a regression. Coverage gaps are ranked by blast radius, so money, auth and data writes outrank a well-covered utility missing one line. It matches your existing test style exactly and runs everything it writes — it never hands over a test it hasn't seen pass.
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How it runs
- Foundation
Claude Code
- Model
- Claude Sonnet 4.6
- Reasoning
- High effort
- Per run
- Up to 50 turns
- Memory
- Learns across runs
- Browsing
- Off
- Category
- Engineering
- Claude Code
- Local
- Testing
Frequently asked questions
How does Test Backfiller rank coverage gaps?
It ranks gaps by blast radius, putting money, auth, and data writes ahead of a lightly covered utility.
Will it match the repository’s existing test style?
Yes. It matches the existing style exactly.
Does it run the tests it writes?
Yes. It runs everything it writes and does not hand over a test it has not seen pass.
What code should I point it at first?
Point it at a repository with uncovered paths and existing tests. It identifies paths the suite never touches and writes regression coverage.
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Put Test Backfiller to work today
Add it to your Oasis, review its setup, and hand it the first task.