private AnimatedDrawableBackend createAnimatedDrawableBackendMock(final int frameCount) {
    // For decoding preview frame, expect some calls.
    final AnimatedDrawableBackend mockAnimatedDrawableBackend = mock(AnimatedDrawableBackend.class);
    when(mockAnimatedDrawableBackend.getFrameCount()).thenReturn(frameCount);
    when(mockAnimatedDrawableBackend.getWidth()).thenReturn(50);
    when(mockAnimatedDrawableBackend.getHeight()).thenReturn(50);
    return mockAnimatedDrawableBackend;
  }
Creates the mock for the AnimatedDrawableBackend with the number of frame

@param frameCount The number of frame to mock
animated-gif/src/test/java/com/facebook/imagepipeline/animated/factory/AnimatedImageFactoryGifImplTest.java