Introduction to jest
- 1. PAVITHRA KODMAD | DEVELOPER Introduction to Jest
- 3. Why Jest?
- 4. Why Jest? Sandboxed Tests Feedback loop One stop shop Community Sandboxed Tests • Tests run in parallel • No shared state between tests
- 5. Why Jest? Sandboxed Tests Feedback loop One stop shop Community Better Feedback loop • Rich CLI • Pretty logging • Better error outputs • Failed tests run first • Coverage
- 6. Why Jest? Sandboxed Tests Feedback loop One stop shop Community One stop shop
- 7. Why Jest? Sandboxed tests Feedback loop One stop shop Community Community Back in 2015 👇
- 8. Why Jest? Sandboxed tests Feedback loop One stop shop Community Community Now 👇
- 9. Why Jest? Sandboxed tests Feedback loop One stop shop Community Community
- 10. Why Jest? Sandboxed tests Feedback loop One stop shop Community Community • Atlaskit actively using and developing tools on Jest • Jest codemods
- 11. Anatomy of a test
- 12. What’s different? • Globals - describe/expect/test
- 16. How to mock?
- 17. How to mock?
- 18. Mock Hoisting Hoists mocks to top of file by default Prevent with doMock
- 19. Spy behavior jest.spyOn always called the spied function.
- 20. Tip : toBe() vs toEqual()
- 21. Tip : jest.resetModules Call to clear any pending state in module cache between tests
- 25. Tip : mockFn.mock.instances Useful to get the source mockImplementation
- 26. Tip : jest.isMockFunction() Useful to check!
- 27. Tip : coverage and coverage thresholds
- 28. Tip : Snapshot Testing Can take snapshots of • Components • Json • String • Anything serializable
- 29. Tip : —runInBand Jest always run in parallel • Makes it run on a single thread • Easier to debug
- 30. Tip : Vscode and Jest
- 31. Tip :Async testing Very similar to what we had with Mocha and Chai
- 32. Cheers to “Painless” testing
- 33. References • Jest Documentation - https://github.com/kalcifer/awesome-jest • Jest as a Platform - https://github.com/rogeliog/jest-as-a-platform-talk/blob/maste Jest%20as%20a%20Platform.pdf • Jest historically - http://rea.tech/painless-javascript-testing-surely-you-jest/ • Jest codemods - https://github.com/skovhus/jest-codemods • Chai and Jest Matchers - https://medium.com/@RubenOostinga/combining-chai- matchers-d12d1ffd0303 • VsCode Jest - https://github.com/orta/vscode-jest • Jest codemods and Sinon - https://github.com/skovhus/jest-codemods/issues/68 • Manjula Dube for this slide - https://twitter.com/manjula_dube/status/9402921548
- 34. Thank you