Features
- Add browser mode for test runner. By default tests are running in headless mode, what is faster. But now one can switch to browser mode and see what is really happening on the page while tests are being executed
Bug fixes
- Main menu has no state, but it was still indicating the last selected item as active one, what brought to confusion.
- env variable to trigger browser mode changed to RUN_IN_BROWSER, it was DEBUG and conflicted with debug pkg widely used (e.g. in puppeteer)