fn verify_reflow(
        content: &'static str,
        expected: &'static str,
        max_line_width: usize,
        unbreakables: Vec<Range>,
        indentations: Vec<usize>,
    ) {
        let indentations = indentations
            .into_iter()
            .map(|n| Indentation::<'static>::new(n))
            .collect::<Vec<_>>();
        let expected = expected
            .lines()
            .enumerate()
            .map(|(idx, line)| (idx + 1, line));

        let mut gluon = Gluon::new(content, max_line_width, &indentations);

        gluon.add_unbreakables(unbreakables);

        for ((line_no, line_content, _), (expected_no, expected_content)) in
            gluon.clone().zip(expected.clone())
        {
            assert_eq!(line_no, expected_no);
            assert_eq!(dbg!(line_content), dbg!(expected_content));
        }

        assert_eq!(dbg!(gluon).count(), expected.count());
    }
`indentations` represent the indentation of individual lines in
`content`.
src/reflow/iter.rs