Custom List class.

CustomList.java

public class CustomList extends AbstractList<MyElement> {

    private List<MyElement> list = null;

    public CustomList() {
        list = new ArrayList<MyElement>();
    }

    @Override
    public MyElement get(int index) {
        return list.get(index);
    }

    @Override
    public boolean add(MyElement e) {
        list.add(list.size(), e);
        return true;
    }

    @Override
    public int size() {
        return list.size();
    }
}

CustomListTest.java

public class CustomListTest {

    @Test
    public void CustomListインスタンスにCustomElementインスタンスを追加できること() {
        String sample = "test";
        CustomElement e = new CustomElement(sample);
        CustomList list = new CustomList();
        list.add(e);
        assertThat(list.size()).isEqualTo(1);
        assertThat(list.get(0).getText()).isEqualTo("test");
        for(CustomElement e : list) {
            assertThat(e.getText()).isEqualTo("test");
        }
    }
}