@Test
public void testGetContractInterface() {

  // given
  final ContractOperation mockOperation = mock(ContractOperation.class);
  when(mockOperation.getContractInterface(any(ContractAddress.class)))
      .thenReturn(ContractInterface.newBuilder().build());
  final AergoClient mockClient = mock(AergoClient.class);
  when(mockClient.getContractOperation()).thenReturn(mockOperation);
  final ClientProvider mockClientProvider = mock(ClientProvider.class);
  when(mockClientProvider.getClient()).thenReturn(mockClient);
  // then
  final QueryApi queryApi = new QueryApiImpl(mockClientProvider);
  final ContractInterface contractInterface = queryApi.getContractInterface(anyContractAddress);
  assertNotNull(contractInterface);
}