The best way to run the Code tests is from the terminal. To make development changes to unit tests you need to be running gulp. See Development Workflow for more details. From the vscode folder run:

OS X and Linux

./scripts/test.sh

Windows

scripts\test

To debug tests use --debug when running the test script. Also, the set of tests can be reduced with the --run and --runGlob flags. Both require a file path/pattern. Like so:

./scripts/test.sh --debug --runGrep **/extHost*.test.js

The following command will create a coverage folder at the root of the workspace:

OS X and Linux

./scripts/test.sh --coverage

Windows

scripts\test --coverage