react19-test-patterns

react19-test-patterns is an agent skill from the github/awesome-copilot collection that gives before-and-after patterns for migrating test files to React 19. React 19 changed several things that break older test suites: the act helper must be imported from the right place, the Simulate test utility was removed in favor of fireEvent, the react-dom test-utils imports need cleaning up, and the number of calls made under StrictMode changed. The skill sets the order of work, and it matters. The act import fix comes first because it unblocks everything else. The Simulate to fireEvent replacement follows immediately after it. Then the remaining react-dom test-utils imports are removed, and StrictMode call counts are measured rather than guessed. Async act wrapping comes next, for the remaining warnings that a state update was not wrapped in act. The custom render helper is verified once per codebase rather than in each test. Each step has a concrete before and after example. The skill is useful for teams upgrading a React application and facing a large set of failing tests. It describes mechanical changes, so the results should be checked by running the suite, because a test that passes after a change may now be asserting less than it did. The skill is installed with the skills CLI from the github/awesome-copilot repository. Its skills.sh page showed about 1.2K installs and passing results from three security audits at the time of the scan.…