macro_rules! assert_metrics {
    (
        $metrics:ident,
        $label_1:ident = $value_1:ident,
        $($label_n:ident = $value_n:ident),*
        => $($rest:tt)+
    ) => {
        assert_metrics!(@inner $metrics,
            concat!(
                stringify!($label_1), "=\"", stringify!($value_1), "\"",
                $(",", stringify!($label_n), "=\"", stringify!($value_n), "\""),*,
            ) => $($rest)+
        );
    };
    (@inner $metrics:ident, $labels:expr =>
     $($metric_name:ident = $metric_value:expr),+) => {
        $(
            assert_contains!(
                $metrics.get("/metrics"),
                concat!(
                    stringify!($metric_name),
                    "{", $labels, "} ",
                    stringify!($metric_value)
                )
            );
        )+
    };
}