@Test
public void testJsonValueAsBytes() {

    ZMSFileChangeLogStoreCommon fstore = new ZMSFileChangeLogStoreCommon(FSTORE_PATH);
    ObjectMapper mapper = Mockito.mock(ObjectMapper.class);
    Mockito.when(mapper.writerWithView(Struct.class)).thenThrow(new RuntimeException("invalid class"));
    fstore.jsonMapper = mapper;
    Struct testStruct = new Struct();
    testStruct.putIfAbsent("key", "value");
    assertNull(fstore.jsonValueAsBytes(testStruct, Struct.class));
}