Great question, @amt! I've broken this out into a dedicated thread, because it sounds like your enquiry about VS Code is just a piece of the puzzle.
I'm hoping to get more context about your specific goals, as "testing" is a broad topic. We've long thought about the best way to write tests within Retool and actually came close to shipping a few different solutions. Nothing has stuck, though.
We currently recommend writing E2E webdriver tests using a tool like Playwright or Cypress.