What is the best way do integration test for Android google map

My application consist mainly of a single Google Map where I display several marker depending on some user action.

for example:

• User press button
• The app contact an external service
• The get the results and display Markers on the Google Map

I would to know what is the best way to test this on Android? I would 'not' like to mock the external service

I have seen Espresso but apparently based on other SO question cannot access Marker? Has this Changed in newer version?