waitForEmulator.gradle

def waitForEmulatorReady() {
    def bootanim = ''
    def failCounter = 0
    while (!(bootanim =~ /stopped/)) {
        def adbProcess = 'adb -e shell getprop init.svc.bootanim'.execute()
        def errCode = adbProcess.waitFor()
        if (errCode != 0) {
            failCounter += 1
            if (failCounter > 3) {
                throw new RuntimeException('failed to start emulator')
            }
        }
        bootanim = adbProcess.text
        println bootanim
        sleep(1000)
    }
}    

android.testVariants.all { variant ->
    variant.connectedInstrumentTest.doFirst {
        waitForEmulatorReady()
    }
}