Question

I am beginer in unit testing.
I use JUnit and Mockito. This is one example method which I want to test.

public List<Person> getPeopleList(List<Aggregate<Person>> aggregateList) {
    List<Person> resultList = new ArrayList<Person>();
    for (Aggregate<Person> aggregate : aggregateList) {
        resultList.add(aggregate);

        for (Person person : aggregate) {
            resultList.add(person);
        }
    }
    return resultList; // the result is person and aggregate list
}

I tried to many ways, but I can’t do it well. Example:

@Test
public void getPeopleListTest(){
    ClassUnderTest testedClass = new ClassUnderTest();

    Aggregate aggregate = mock(Aggregate.class);
    Iterator<Aggregate<Person>> aggregateIterator = mock(Iterator.class);
    when(aggregateIterator.hasNext()).thenReturn(true, false);
    when(aggregateIterator.next()).thenReturn(aggregate);

    List<Aggregate<Person>> aggregateList = mock(List.class);

    aggregateList.add(aggregate);

    List<Person> list = testedClass.getPeopleList(aggregateList);

    assertEquals(1, list.size());
}

Thank you in advance.

Answer 1

I wouldn’t mock every possible thing. I would only mock the class you want to test and assume List behaves correctly.

public class Main {
    interface Person {
    }

    interface Aggregate<T> extends Person, Iterable<T> {
    }

    public static List<Person> getPeopleList(List<Aggregate<Person>> aggregateList) {
        List<Person> resultList = new ArrayList<Person>();
        for (Aggregate<Person> aggregate : aggregateList) {
            resultList.add(aggregate);

            for (Person person : aggregate) {
                resultList.add(person);
            }
        }
        return resultList; // the result is person and aggregate list
    }

    public static void main(String... args) {
        Aggregate<Person> aggregate = mock(Aggregate.class);
        Aggregate<Person> aggregate2 = mock(Aggregate.class);
        Person person = mock(Person.class);
        Person person2 = mock(Person.class);
        when(aggregate.iterator()).thenReturn(Arrays.asList(person).iterator());
        when(aggregate2.iterator()).thenReturn(Arrays.asList(person2).iterator());

        List<Person> list = getPeopleList(
                Arrays.asList(aggregate, aggregate2));
        System.out.println(list);
        System.out.println("size: " + list.size());
    }
}

prints

[Mock for Aggregate, hashCode: 2037567902, Mock for Person, hashCode: 1629493852, Mock for Aggregate, hashCode: 44220373, Mock for Person, hashCode: 182467149]
size: 4