android jacoco coverage empty with gradle

Question

I'm trying to make jacoco create a code coverage report for my android test project. I have the following in build.gradle:

apply plugin: 'com.android.application'
apply plugin: 'jacoco'
...
jacoco {
    toolVersion = "0.7.1.201405082137"
}
...
android {
    buildTypes {
        release {
        }
        debug {
            testCoverageEnabled true
        }
    }
}

when I run gradlew -i createDebugCoverageReport, I get a coverage report, but it's empty. the end of the gradle execution is as follows:

:androidTest:connectedAndroidTest (Thread[main,5,main]) completed. Took 2 mins 36.951 secs.
:androidTest:createDebugCoverageReport (Thread[main,5,main]) started.
:androidTest:createDebugCoverageReport
Executing task ':androidTest:createDebugCoverageReport' (up-to-date check took 0.006 secs) due to:
  Output file /home/akos/src/androidTest/build/outputs/reports/coverage/debug has changed.
  Output file /home/akos/src/androidTest/build/outputs/reports/coverage/debug/index.html has been removed.
  Output file /home/akos/src/androidTest/build/outputs/reports/coverage/debug/.resources/package.gif has been removed.
[ant:reportWithJacoco] Loading execution data file /home/akos/src/androidTest/build/outputs/code-coverage/connected/coverage.ec
[ant:reportWithJacoco] Writing bundle 'debug' with 3 classes
:androidTest:createDebugCoverageReport (Thread[main,5,main]) completed. Took 0.215 secs.

BUILD SUCCESSFUL

Total time: 4 mins 53.467 secs

and indeed, the coverage.ec file referenced above is empty (of 0 length)

in the directory build/intermediates/coverage-instrumented-classes/ , I seem to have the instrumented class files

this is with gradle 2.1

what am I doing wrong?

Answer 1

Try to generate the debug coverage report using Nexus device (5 or 5x), it will works perfectly. I was facing same issue with Samsung devices (coverage.ec is empty) but after that I run it with Nexus 5x and everything was working fine.

Answer 2

There's a problem in the Android Gradle Plugin 0.14.0 that generates an empty coverage.ec file. It's known and was fixed in a branch but doesn't seem to have made it out to the public yet: https://code.google.com/p/android/issues/detail?id=78556

On the other hand, a lovely workaround template project for Android Studio can be found here using Jacoco and RoboElectric: https://github.com/nenick/android-gradle-template

So you can wait for Google to fix it or use someone else's build library repository, but Android Studio 1.0.0's gradle plugin is useless.