Using a helper macro vs helper function in tests

If we use helper functions then the assert failure will be reported in the function and it will be harder for us to know which call to that function triggered the error.
If we use macro, then we get the line where the macro is called.

Run cargo test to see the difference in error reporting.

examples/macros/test-failure-report/src/lib.rs

pub fn calc(a: i32, b: i32) -> String {
    format!(
        r#"
    <html>
    <head>
    <title>Calc</title>
    </head>
    <body>
    <h1>Results</h1>
    <div id="add">{}</div>
    <div id="multiply">{}</div>
    </body>
    </html>
    "#,
        a * b,
        a + b
    )
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_good() {
        let html = calc(2, 2);
        check_html_function(&html, "title", "Calc");
        check_html_function(&html, "h1", "Results");
        check_html_function(&html, "#add", "4");
        check_html_function(&html, "#multiply", "4");
        check_html_macro!(&html, "title", "Calc");
        check_html_macro!(&html, "h1", "Results");
        check_html_macro!(&html, "#add", "4");
        check_html_macro!(&html, "#multiply", "4");
    }

    #[test]
    fn test_bad_add_func() {
        let html = calc(3, 3);
        check_html_function(&html, "title", "Calc");
        check_html_function(&html, "#add", "6");
        check_html_function(&html, "h1", "Results");
    }

    #[test]
    fn test_bad_multiply_func() {
        let html = calc(3, 3);
        check_html_function(&html, "title", "Calc");
        check_html_function(&html, "#multiply", "9");
        check_html_function(&html, "h1", "Results");
    }

    #[test]
    fn test_bad_add_macro() {
        let html = calc(3, 3);
        check_html_macro!(&html, "title", "Calc");
        check_html_macro!(&html, "#add", "6");
        check_html_macro!(&html, "h1", "Results");
    }

    #[test]
    fn test_bad_multiply_macro() {
        let html = calc(3, 3);
        check_html_macro!(&html, "title", "Calc");
        check_html_macro!(&html, "#multiply", "9");
        check_html_macro!(&html, "h1", "Results");
    }

    fn check_html_function(html: &str, css_selector: &str, expected: &str) {
        let document = scraper::Html::parse_document(html);
        let selector = scraper::Selector::parse(css_selector).unwrap();
        assert_eq!(
            &document.select(&selector).next().unwrap().inner_html(),
            expected
        );
    }

    macro_rules! check_html_macro {
        ($html: expr, $selectors: expr, $text: expr) => {{
            let document = scraper::Html::parse_document($html);
            let selector = scraper::Selector::parse($selectors).unwrap();
            assert_eq!(
                &document.select(&selector).next().unwrap().inner_html(),
                $text
            );
        }};
    }
    pub(crate) use check_html_macro;
}


running 5 tests
test tests::test_bad_add_func ... FAILED
test tests::test_bad_add_macro ... FAILED
test tests::test_bad_multiply_macro ... FAILED
test tests::test_bad_multiply_func ... FAILED
test tests::test_good ... ok

failures:

---- tests::test_bad_add_func stdout ----
thread 'tests::test_bad_add_func' panicked at src/lib.rs:69:13:
assertion `left == right` failed
  left: "9"
 right: "6"

---- tests::test_bad_add_macro stdout ----
thread 'tests::test_bad_add_macro' panicked at src/lib.rs:54:9:
assertion `left == right` failed
  left: "9"
 right: "6"
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- tests::test_bad_multiply_macro stdout ----
thread 'tests::test_bad_multiply_macro' panicked at src/lib.rs:62:9:
assertion `left == right` failed
  left: "6"
 right: "9"

---- tests::test_bad_multiply_func stdout ----
thread 'tests::test_bad_multiply_func' panicked at src/lib.rs:69:13:
assertion `left == right` failed
  left: "6"
 right: "9"


failures:
    tests::test_bad_add_func
    tests::test_bad_add_macro
    tests::test_bad_multiply_func
    tests::test_bad_multiply_macro

test result: FAILED. 1 passed; 4 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s