@Test
public void testAppend() throws IOException {

  when(mockDataClient.readModifyWriteRowAsync(any(ReadModifyWriteRow.class))).thenReturn(future);
  BigtableBufferedMutator underTest = createMutator(new Configuration(false));
  underTest.mutate(new Append(EMPTY_BYTES).add(EMPTY_BYTES, EMPTY_BYTES, EMPTY_BYTES));
  verify(mockDataClient, times(1)).readModifyWriteRowAsync(any(ReadModifyWriteRow.class));
}