@Test
    public void manyInsertsResizesArray() {
        String expected = "";
        for (int i = 0; i < 100; i++) {
            a.insert(new Vertex(i));
            expected += i + " ";
        }
        String actual = "";
        for (int i = 0; i < 100; i++) {
            actual += a.get(i).getId() + " ";
        }
        assertEquals(expected, actual);
    }