def test_unpopularItems_5():
    assert unpopularItems([]) == []
def test_unpopularItems_4():
    assert unpopularItems([i2, i4]) == [i2, i4]
def test_unpopularItems_2():
    assert unpopularItems([i1, i2]) == [i2]
def test_unpopularItems_3():
    assert unpopularItems([i4, i3, i2, i1]) == [i4, i2]
def test_unpopularItems_1():
    assert unpopularItems([i1, i3]) == []