Rust Testing

A test suite is a statement about which changes the team refuses to accept silently. This skill decides what deserves a test and in which form — the five ordinary forms, golden files for file-shaped artifacts, and differential for ports — and it never decides what the code under test should look like. Shaping the code belongs to the craft skills; whether a change is tested at all, as a review verdict, is /rust-code-review.

What a test is for

A test exists to fail when behaviour changes. A test that restates the implementation — asserting that a getter returns the field it was handed — fails when the code is refactored and passes when the behaviour breaks, which is exactly backwards. Before writing a test, name the regression it would catch in one sentence. If that sentence is "the code changed," do not write the test.

Pick the form from what is being asserted