5. writing-unit-tests.md

Contribution Guide

1. Getting Set up
2. Building Samples and Packages
3. Running a Sample or Storybook
4. Testing your changes
5. Writing unit tests
6. Submitting a PR
7. Having your changes published

5. Writing unit tests

Our unit tests are written using Jest.

Tips for writing unit tests

• All unit tests must be in a .test.ts or .test.tsx file - jest will automatically pick up these files and run them.

• Unit tests must be well named and test only one thing per test.

• Unit tests must follow the Arrange, Act, Assert pattern, e.g.

  test("addOne function should add one to a given number", () => {
      // Arrange
      const givenNumber = 5;
  
      // Act
      const result = addOne(givenNumber);
  
      // Assert
      expect(result).toEqual(6);
  });

  • This ensures good structure to unit tests making them easily understandable for the developer who needs to take a look at them when they do not pass.

• UI components must have snapshot tests (see Update test snapshots below)

Running unit tests

To run unit tests for the package or sample you are in:

rushx test # run this from the package directory

To run all unit tests for the whole repo

rush test # this can be run from anywhere

Update test snapshots

If you have made changes to any UI components, or added a new UI component, you will need to update the snapshots.

For more information on what snapshots are, see the official Jest snapshot documentation.

To update snapshots after changing a UI component, in your package directory, run:

rushx snapshot:update

Debugging unit tests

Documentation to follow.

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