l.PushBack(3)
	l.InsertBefore(1, new(a.Element[int]))
	checkList(&l, []interface{}{1, 2, 3})
}

// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
func TestInsertAfterUnknownMark() {
	var l a.List[int]
	l.PushBack(1)
	l.PushBack(2)
	l.PushBack(3)
	l.InsertAfter(1, new(a.Element[int]))
	checkList(&l, []interface{}{1, 2, 3})
}

	l.PushBack(3)
	l.InsertBefore(1, new(_Element[int]))
	checkList(&l, []interface{}{1, 2, 3})
}

// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
func TestInsertAfterUnknownMark() {
	var l _List[int]
	l.PushBack(1)
	l.PushBack(2)
	l.PushBack(3)
	l.InsertAfter(1, new(_Element[int]))
	checkList(&l, []interface{}{1, 2, 3})
}

	l.PushBack(3)
	l.InsertBefore(1, new(Element))
	checkList(t, &l, []any{1, 2, 3})
}

// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
func TestInsertAfterUnknownMark(t *testing.T) {
	var l List
	l.PushBack(1)
	l.PushBack(2)
	l.PushBack(3)
	l.InsertAfter(1, new(Element))
	checkList(t, &l, []any{1, 2, 3})
}