Probably fixes the first point in #8942
My guess is that the mockExpressionUpdate may be not set in cases when the test runs before App mounting. To make sure all the setup is done, we wait for `App` widget to being mounted before proceeding.
# Important Notes
This PR also change the way we run test's server. Before it was always a production build, but this makes development iteration long. Now we test production build only on CI or when `PROD=true` env variable is set.
- Closes#8179
# Important Notes
- ⚠️ These tests are currently *not run* on any CI workflow.
- There is some unused code for mocking the PM. This has been intentionally kept, as this may be useful in the future.
Note that this may be useful for testing the dashboard, however the dashboard is currently only tested in cloud mode
- that is, without the backend switcher, and with only the remote backend available. As such, currently it uses HTTP API mocks, and no PM mock.
