rust-write-tests
This skill contains shell command directives (!`command`) that may execute system commands. Review carefully before installing.
Rust Test Writing Skill
Write tests that catch real bugs. Every test must guard a specific invariant -- not just prove the code "works."
The "What Could Break?" Framework
Before writing any test, answer these four questions:
- What invariant does this code maintain? (e.g., "deserialized config always has a default profile")
- What edge case would violate it? (e.g., "empty TOML table, missing key, extra unknown key")
- What platform difference could surface? (e.g., "path separators, case sensitivity, symlink behavior")
- What would a future refactor accidentally break? (e.g., "field added to struct but not to Display impl")
If you can only answer #1, your test is a happy-path test. Answer all four and you have a regression suite.
The 5 Test Transformations
Each transformation shows a superficial test pattern and its expert replacement.
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