Robolectric has the ability to run tests against multiple variations of android. It appears that for most of our testing we use @Config(sdk = Build.VERSION_CODES.X) which runs the tests against one android version. Roboletric also supports minSdk which will use the value as a min and run for all following version codes.
In addition it appear that maps set the SDK to android "P" when the underlying maps sdk supports back to 21.

Convert all robolectric tests in google_maps_android to use minSdk and set the minSdk to the lowest value possible. Document the work arounds or things you learned so that when we do this change to other platforms it goes smoother.

Related comment thread: flutter/packages#7313 (comment)

Documentation also says it supports android api 20 and above which is incorrect given the min version of android flutter supports is api 21. https://pub.dev/packages/google_maps_flutter