Date: 2019-05-24
Superceded by 10. Integration tests
VS Code has documented how to test an extension in integration with VS Code API.
These tests will run inside a special instance of VS Code named the
Extension Development Host, and have full access to the VS Code API.
But VS Code test runner is adapted to be used with mocha or Jasmine.
For unit tests, we want to use Jest. But Jest and mocha have conflicting types, preventing TS to build. A solution would have been to create a custom test runner for VS Code API, that would run integration tests with Jest. But we didn't managed to create one that works.
That's partly because Jest doesn't have an official way to run tests programatically. We weren't able to make VS Code test runner work with Jest runCLI() (async) method.
Also, integration tests are not the most important part of the project for the moment.
We won't do integration tests. We'll rely on unit tests (e.g. state-based tests, collaboration tests and contract tests).
We can use Jest to write (unit) tests.
Tests will run fast. They will be easy to write and maintain.
We won't be able to automatically test the extension with the actual VS Code API.