Reminder to compile between tests

test/unit/README.md

@@ -8,6 +8,7 @@ All unit tests are run inside a electron-browser environment which access to DOM
 
 - use the `--debug` to see an electron window with dev tools which allows for debugging
 - to run only a subset of tests use the `--run` or `--glob` options
+- use `yarn watch` to automatically compile changes
 
 For instance, `./scripts/test.sh --debug --glob **/extHost*.test.js` runs all tests from `extHost`-files and enables you to debug them.