We have set up a sample Android project with Espresso tests. You can find it right here. The project is built on CircleCI right here.
We had a few reports around Espresso not being able to run because of the locked screen on the emulator—the issue is resolved in this sample build by adding a little wait time between the end of the emulator boot process and issuing the screen unlock command via adb.
Please check out the README file in the repository, plus the circle.yml and global and module-specific build.gradle files for details.