Run using official jacoco 0.8.7:

./gradlew app:testDebugUnitTestCoverage

Run using forked jacoco:

./gradlew app:testDebugUnitTestCoverage -PuseFork

Open report (OS X):

open app/build/reports/jacoco/testDebugUnitTestCoverage/html/index.html

Saved reports run on my machine:

• Forked reports/testDebugUnitTestCoverageFork/html/index.html
• 0.8.7 reports/testDebugUnitTestCoverageJacoco/html/index.html