Android Studio JaCoCo reports 0% coverage

Question

I use this build.gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "22.0.1"

    defaultConfig {
        applicationId "name"
        minSdkVersion 21
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        debug {
            testCoverageEnabled = true
        }
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    testOptions {
        unitTests.returnDefaultValues = true
    }
}


dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    testCompile 'org.mockito:mockito-core:1.10.19'
    compile 'com.android.support:appcompat-v7:23.1.0'
    compile 'com.android.support:support-v4:23.1.0'
    compile 'com.android.support:design:23.1.0'


}

The coverage report shows that my tests are successful but with a 0% coverage. That is impossible. I just want to get a combined coverage of junit test and android instrumentation tests. Can anyone tell me what is wrong?