Testing ui-kit components

Here is the guide how to set up testing with Vitest and Vue Test Utils for the Acronis UI Component Library.

Unit testing

We use Vue Test Utils for Vue.js 3 and Vitest for unit testing. When writing tests, we try to maintain at least 80% code coverage by tests.

Testing vue components

We mostly use the composition API to write components. Therefore, the way components are tested must also be modern.

What we test when creating and updating components:

• Checking that the component is rendered correctly (snapshots and node contents):
  • when props change
  • when the state changes
  • when interacting with the user
  • when interacting with other components
  • when interacting with the API
  • when interacting with the repository
  • when interacting with the router
  • when interacting with external libraries
• We check that the component behaves correctly (method calls, emits, provide, state changes)

General approach when writing a unit test:

• Arrange phase, Create and Mount a component;
• Act phase, Changing the state or simulating user interaction;
• Assert phase, Check the result

Visual regression testing with Cypress

Visual regression testing is a technique to verify that the changes in the codebase do not affect the visual appearance of the application. For that purpose we mount test components(packages/examples/demos) and take screenshots(packages/ui/cypress/snapshots) of them. Then we compare the screenshots with the baseline screenshots. To run visual regression tests with Cypress, you need to run the following command:

pnpm run cypress:run

We must run regression tests in the same environment as the development environment. Generated snapshots are used as a baseline for comparison. Reference images taken in a docker environment are used for comparison. To do this, we need to run cypress in docker container:

// Prepare the environment
pnpm run cypress:docker:build

// Run the tests and update snapshots
pnpm run cypress:docker:run

In GitHub Actions, we run the tests in the same way. We use visual-regression.yml workflow for this. You can run the workflow manually in the GitHub Actions tab or locally with act from the root directory.

act -j visual-regression

Performance tests

TBD