chore: improve docs on testing (#2456)

Author: czosel

CONTRIBUTING.md

@@ -10,14 +10,14 @@ yarn test
 yarn prettier path/to/file.php`
 
 # run a single test
-yarn test tests/{folder of your choice}
+yarn test:node tests/{folder of your choice}
 ```
 
 Here's what you need to know about the tests:
 
 - The tests use [Jest](https://facebook.github.io/jest/) snapshots.
-- You can make changes and run `jest -u` (or `yarn test -u`) to update the snapshots. Then run `git diff` to take a look at what changed. Always update the snapshots when opening a PR.
-- You can run `AST_COMPARE=1 yarn test` for a more robust test run. That formats each file, re-parses it, and compares the new AST with the original one and makes sure they are semantically equivalent.
+- You can make changes and run `jest -u` (or `yarn test:node -u`) to update the snapshots. Then run `git diff` to take a look at what changed. Always update the snapshots when opening a PR.
+- You can run `AST_COMPARE=1 yarn test:node` for a more robust test run. That formats each file, re-parses it, and compares the new AST with the original one and makes sure they are semantically equivalent.
 
 Run `yarn lint --fix` to automatically format files.