Tests for JavaScript in the Blocks plugin are powered by [Jest](https://jestjs.io/).
The Blocks plugin follows the same patterns as Gutenberg, therefore for instructions on writing tests you can [refer to this page in the Gutenberg Handbook](https://developer.wordpress.org/block-editor/contributors/develop/testing-overview/).
These tests are all run automatically on open PRs by Travis CI.
All the following tests require that the dependencies are installed (`npm install` `composer install`). Ensure you've followed the [Getting Started Guide](getting-started.md) to set up node and other dependencies before running any tests.
## How to run JavaScript unit tests
Unit tests are implemented near the code they test, in `*.test.js` files.
Since these drive the user interface, they need to run against a test environment - i.e. a web server running WordPress, Woo and blocks plugin, with a known state/configuration.
When you're iterating on a new test you'll often run this repeatedly, as you develop, until your test is just right.
When you're done, you may want to shut down the test environment:
-`npm run wp-env stop` to stop the test environment
**Note:** There are a number of other useful `wp-env` commands. You can find out more in the [wp-env docs](https://github.com/WordPress/gutenberg/blob/master/packages/env/README.md).
### Modify the local environment used by end-to-end tests
To modify the environment used by tests locally, you will need to modify `.wp-env.json`. For example, you can set a specific WP version and install the latest Gutenberg version with these two lines:
We follow the same WordPress support policy as WooCommerce, this means we need to support the latest version, and the two previous ones (L-2).
For that, we run end-to-end tests against all of those versions, and because we use packages published by Gutenberg, we also run tests against the latest version of Gutenberg plugin.
