@Test(expectedExceptions=NullPointerException.class)
public void convertToReference_NULL_matchableEntity() {

    
    // given
    
    IdWithSimilarity idWithSimilarity = Mockito.mock(IdWithSimilarity.class);
    Tuple2<MatchableEntity, IdWithSimilarity> entityWithId = new Tuple2<>(null, idWithSimilarity);
    
    // execute
    
    matchableEntityWithSimilarityConverter.convertToReference(entityWithId);
    
}