Encapsulate repetitive API testing rules into SKILL.md so AI generates test cases to standard

Using the example of team testers who repeat API testing rules to AI every day, the author wrote roughly 300 words of rules—covering logging in to get a token, three-layer assertions, and an exception scenario checklist—into SKILL.md. After encapsulation, one only needs to say "use api-test-standard to test this API," and the assertion layers and exception coverage stay consistent, while colleagues can also reuse the same set of rules. The article presents a four-step encapsulation method: record the most frequently repeated words verbatim; split into preconditions and execution steps, assertions, and exceptions; turn vague statements into executable rules; and add a self-check checklist at the end. It also lists five pitfalls, including writing it as a colloquial chat log, SKILL.md exceeding 500 lines, writing too empty a description, not verifying after writing, and only encapsulating without iterating.