Faster test & Build of Android Studio Project (Gradle Project) on Circle-CI.

circle.yml

machine:
  java:
    version: oraclejdk8
  environment:
    # Java options
    JAVA_OPTS: "-Xms512m -Xmx2048m"
     # ADB options
    ADB_INSTALL_TIMEOUT: 5000

dependencies:
  pre:
    # Install the android packages
    - echo y | android update sdk --no-ui --all --filter "extra-google-market_licensing,extra-google-play_billing"
    #  [HINT] Almost packages are pre installed: https://circleci.com/docs/build-image-precise/#android
  post:
    # Create the android emulator
    - echo n | android create avd -n test_android_17 -f -t android-17
    #  [HINT] Circle-CI already have built-in emulator (circleci-android22), but it's so heavy.
    # Make a SD Card image file for the android emulator
    - mksdcard -l e 128M sdcard.img

test:
  pre:
    # Start the android emulator
    - emulator -avd test_android_17 -no-audio -no-boot-anim -no-window -sdcard sdcard.img:
        background: true
        parallel: true
    # Start the adb server
    - fb-adb start-server:
        background: true
  override:
    # Generate a debug-apk
    - ./gradlew assembleDebug -PdisablePreDex
    #  [Hint] About -PdisablePreDex, please see http://tools.android.com/tech-docs/new-build-system/tips#TOC-Improving-Build-Server-performance.
    # Wait for emulator to boot
    - circle-android wait-for-boot; sleep 5
    # Pre-install the app (debug-apk)
    - fb-adb install app/build/outputs/apk/app-debug.apk
    # Allow the SET_ANIMATION_SCALE permission to the app
    - fb-adb shell pm grant "${APP_PACKAGE_NAME}" android.permission.SET_ANIMATION_SCALE
    # Unlock the emulator screen
    - fb-adb shell input keyevent 82
    # Install the app (test-apk) and Run the tests
    - ./gradlew connectedDebugAndroidTest -PdisablePreDex --stacktrace
    # Save a screenshot to Circle-CI Artifacts
    - fb-adb rcmd screencap -p > $CIRCLE_ARTIFACTS/screen-$(date +"%T").png
    # Copy the generated apk files to Circle-CI Artifacts
    - cp -r app/build/outputs/apk/ $CIRCLE_ARTIFACTS
    # Copy the test results to Circle-CI Artifacts
    - cp -r app/build/outputs/androidTest-results/* $CIRCLE_TEST_REPORTS

# [HINT] The following example will upload the generated apk file to Slack and Google Drive 
#deployment:
#  staging:
#    branch: /.*/ # all branch
#    commands:
#      - |
#          # Make a filename of APK
#          export apk_name="build-${CIRCLE_BRANCH}-`git rev-parse --short HEAD`.apk"
#          # Upload the APK file to Slack
#          curl https://slack.com/api/files.upload -F token="${SLACK_TOKEN}" -F channels="${SLACK_CHANNEL}" -F title="${apk_name}" -F filename="${apk_name}" -F file=@app/build/outputs/apk/app-debug.apk
#          # Upload the APK file to Google Drive
#          #  [HINT] You can get the refresh token of Google using gdrive command: https://github.com/prasmussen/gdrive
#          curl -L -o gdrive "https://docs.google.com/uc?id=0B3X9GlR6EmbnQ0FtZmJJUXEyRTA&export=download"; chmod u+x gdrive
#          ./gdrive --refresh-token "${GDRIVE_REFRESH_TOKEN}" upload --parent "${GDRIVE_DIR_ID}" --name "${apk_name}" app/build/outputs/apk/app-debug.apk