write-tests

name	write-tests
description	Writing tests that catch regressions instead of restating the code. Use when adding tests, when a fix needs a regression test, or when the user asks for coverage.

Write tests

1. Copy the house style first. Open the nearest existing test file and match its layout, naming, helpers, and assertion style. A test that looks foreign gets rewritten in review.
2. Name tests as behaviors, hierarchically. timeout_keeps_partial_output, edit_mismatch_embeds_closest_region: the name states the guarantee, and a shared prefix groups the family for filtered runs.
3. Test the behavior, not the implementation. Assert on outputs and effects, not on private state or call counts. A test that breaks on every refactor protects nothing.
4. Every bug fix ships its regression test. Write the test first, watch it fail for the right reason, then fix. A test that never failed proves nothing.
5. One behavior per test. Three asserts about one outcome is fine; three scenarios in one test means the name lies about two of them.
6. Cover the edge that motivated the code. Empty input, the boundary value, the error path. The happy path usually already works.
7. Run the new tests plus the file's old ones, and quote the counts in your report.