unable to run webrtc unittests on android device connected to Ubuntu 14.04 desktop

[test9111]

 webrtc/build/android/test_runner.py gtest -s video_capture_tests gave me an error "Could not find apk or executable for video_capture_testsE    0.013s Main  Unrecognized error occurred."

any clue what could be wrong in my setup. I was able to compile apks like apprtc and webrtcdemo

~/android_webrtc/src$ webrtc/build/android/test_runner.py gtest -s video_capture_tests

Could not find apk or executable for video_capture_testsE    0.013s Main  Unrecognized error occurred.

Traceback (most recent call last):

  File "/local/mnt/workspace/android_webrtc/src/build/android/test_runner.py", line 1056, in main

    return RunTestsCommand(args, parser)

  File "/local/mnt/workspace/android_webrtc/src/build/android/test_runner.py", line 938, in RunTestsCommand

    return RunTestsInPlatformMode(args, parser)

  File "/local/mnt/workspace/android_webrtc/src/build/android/test_runner.py", line 974, in RunTestsInPlatformMode

    with test_instance_factory.CreateTestInstance(args, infra_error) as test:

  File "/local/mnt/workspace/android_webrtc/src/build/android/pylib/base/test_instance_factory.py", line 15, in CreateTestInstance

    args, isolator.Isolator(), error_func)

  File "/local/mnt/workspace/android_webrtc/src/build/android/pylib/gtest/gtest_test_instance.py", line 164, in __init__

    error_func('Could not find apk or executable for %s' % self._suite)

  File "/local/mnt/workspace/android_webrtc/src/build/android/test_runner.py", line 968, in infra_error

    parser.exit(status=constants.INFRA_EXIT_CODE, message=message)

  File "/usr/lib/python2.7/argparse.py", line 2351, in exit

    _sys.exit(status)

SystemExit: 87