@Test
public void updateDriveFileWithIdentifier() throws Exception {

    final java.io.File file = new java.io.File("/");
    final String id = "id";
    when(driveDataStreams.updateFile(identifier, file)).thenReturn(Single.just(driveFile));
    when(driveFile.getId()).thenReturn(id);
    final TestObserver<Identifier> testObserver = driveStreamsManager.updateDriveFile(identifier, file).test();
    testObserver.assertValue(new Identifier(id));
    testObserver.assertComplete();
    testObserver.assertNoErrors();
}