public Buffer getBuffer() {
    LOGGER.info("Get current buffer: " + current);
    return frameBuffers[current];
  }
@Test
  void testGetBuffer() {
    try {
      var scene = new Scene();
      var field1 = Scene.class.getDeclaredField("current");
      field1.setAccessible(true);
      field1.set(scene, 0);
      var frameBuffers = new FrameBuffer[2];
      var frameBuffer = new FrameBuffer();
      frameBuffer.draw(0, 0);
      frameBuffers[0] = frameBuffer;
      var field2 = Scene.class.getDeclaredField("frameBuffers");
      field2.setAccessible(true);
      field2.set(scene, frameBuffers);
      assertEquals(frameBuffer, scene.getBuffer());
    } catch (NoSuchFieldException | IllegalAccessException e) {
      fail("Fail to access private field.");
    }
  }