Generate code coverage. If on a mac, the afterTask will open the results in the default browser when you use the openinbrowser=true param.

aftertask.gradle

/* 
# source: https://www.reddit.com/r/androiddev/comments/3ig3gm/show_us_your_gradle_tasks/cugju7z
usage:
./gradlew jacocoTestReport -Popeninbrowser=true #opens in browser
./gradlew jacocoTestReport #does not open in browser
*/
configurations {
    jacocoReport
}

task jacocoTestReport(type: JacocoReport, dependsOn: ['test']) {
    description = "Generates Jacoco coverage reports: XML and HTML"
    group = "Reporting"

    jacocoClasspath = project.configurations['androidJacocoAnt']

    // exclude auto-generated classes and tests
    def fileFilter = ['**/R.class', '**/R$*.class', '**/BuildConfig.*', '**/Manifest*.*', '**/*Test*.*',
                      'android/**/*.*']
    def debugTree = fileTree(dir: "${project.buildDir}/intermediates/classes/debug/<your package tld>/<your package company name>/“, excludes: fileFilter)
    def mainSrc = "${project.projectDir}/src/main/java"
    sourceDirectories = files([mainSrc])
            classDirectories = files([debugTree])
            executionData = fileTree(dir: project.projectDir, includes: ['**/*.exec', '**/*.ec'])

            reports {
        xml {
            enabled = true
            destination = "${project.buildDir}/reports/jacoco/test/jacocoTestReport.xml"
        }
        csv.enabled false
        html {
            enabled = true
            destination = "${project.buildDir}/reports/jacoco"
        }
    }
}

dependencies {
    jacocoReport 'org.jacoco:org.jacoco.ant:0.7.2.201409121644'
}

gradle.taskGraph.afterTask { Task task, TaskState state ->
    if (state.failure) {
        println "-- jacocoTestReport FAILED."
    } else {
        if (task.name == "jacocoTestReport") {
            def jacocoHTMLIndex = "${project.buildDir}/reports/jacoco/index.html"
            def openinbrowser = project.hasProperty('openinbrowser') ? project.getProperty('openinbrowser') : 'false'
            if (openinbrowser == "true") {
                exec {
                    commandLine 'open', jacocoHTMLIndex
                }
            }else{
                println "Generated jacocoTestReport html located at ${jacocoHTMLIndex}"
            }
        }
    }
}