Method metadata

crates/test/src/lib.rs:1176–1179

(mut self, name: &'a str, value: impl fmt::Display)

    }

    fn metadata(mut self, name: &'a str, value: impl fmt::Display) -> Self {
        self.metadata.push((name, value.to_string()));
        self
    }
}

/// Helper trait for each language to implement which encapsulates