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34 lines
1.3 KiB
Markdown
34 lines
1.3 KiB
Markdown
# Step 2.4
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[Lessons](../) | [Exercise](./exercise/) | [Demo](./demo/)
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Testing Typescript code with jest. jest is a test framework made by Facebook and is very popular in the React and the wider JS ecosystem. We will work on implementing simple unit tests here in this exercise.
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https://jestjs.io/
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- Multi-threaded and isolated test runner
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- Provides a "fake" browser environment if needed (window, document, DOM, etc).
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- Snapshots: show API or large object changes along side code changes in pull requests
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- Code coverage is integrated (--coverage)
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- Very clear error messages of where the test failures occur
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# Demo
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In this repo, we can start an inner loop development of tests with the command: `npm test`
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Take a look at code inside `demo/src`:
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1. `index.ts` is exports a few functions for a counter as well as a test for squaring numbers but demonstrates out jest uses mocks
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2. `multiply.ts` is a contrived example of a function that is exported
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3. `index.spec.ts` is the test file: note how tests are re-run on save to test file changes as well as source code changes under `src`
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# Exercise
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1. Run the tests by running `npm test` at the root of the bootcamp project
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2. Look at the `stack.ts` for a sample implementation of a stack
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3. Follow the instructions inside the `stack.spec.ts` file to complete the two tests
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