How to get text from Progress Dialog using Flutter Test Driver

I have a Flutter Application. Currently I am trying to make an automated integration tests using Test Driver.

This is what I am trying to do.

Scenario:
- Click on Button
- Check if the Progress Dialog appeared

I was wondering if it is somehow possible to get the boolean value of the second step. I was trying to do methods like these:

Future<bool> loadingIndicatorVisible () async {
    var a = _driver.waitFor(find.byType("ProgressDialogType.Normal"));    
  }

but I was not able to do this with mentioned method.

This progress dialog has text "Loading...", but I was not able to do this with find.text either.

Is there any way to do this correctly?