// When newInput is set back to null
        item.setNewInput(null);
        assertEquals("original", item.toLineString());
    }

    @Test
    public void test_toLineString_withEmptyInput() {
        // Test toLineString with empty original input
        StopwordsItem item = new StopwordsItem(1, "");
        assertEquals("", item.toLineString());

        item.setNewInput("new");

        // Test with item created with id=0
        ProtwordsItem newItem = new ProtwordsItem(0, "newword");
        assertEquals("newword", newItem.toLineString());
    }

    @Test
    public void test_toLineString_withEmptyInput() {
        // Test toLineString with empty input
        ProtwordsItem item = new ProtwordsItem(1, "");
        assertEquals("", item.toLineString());

        assertEquals("new1,new2,new3=>newOutput", item.toLineString());
    }

    @Test
    public void test_toLineString_withSingleInput() {
        String[] inputs = { "single" };
        CharMappingItem item = new CharMappingItem(1L, inputs, "output");

        assertEquals("single=>output", item.toLineString());
    }

    @Test
    public void test_toLineString_withEmptyInputs() {

        // Debug: print what we actually got
        if (result.size() > 0) {
            for (CharMappingItem item : result) {
                System.out.println("Unexpected item: " + item.toLineString());
            }
        }

        // An empty file should return no items
        assertEquals("Empty file should have no items", 0, result.size());