Add the first use of the rust benchmark tests.

src/parser/keyword.rs

@@ -250,3 +250,25 @@ fn export_keyword<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, OrgSource<'s>>
         take_while1(|c: char| c.is_alphanumeric() || "-_".contains(c)),
     )))(input)
 }
+
+#[cfg(test)]
+mod tests {
+    use test::Bencher;
+
+    use super::*;
+    use crate::context::Context;
+    use crate::context::ContextElement;
+    use crate::context::GlobalSettings;
+    use crate::context::List;
+    use crate::parser::OrgSource;
+
+    #[bench]
+    fn bench_affiliated_keyword(b: &mut Bencher) {
+        let input = OrgSource::new("#+CAPTION[*foo*]: bar *baz*");
+        let global_settings = GlobalSettings::default();
+        let initial_context = ContextElement::document_context();
+        let initial_context = Context::new(&global_settings, List::new(&initial_context));
+
+        b.iter(|| assert!(affiliated_keyword(&initial_context, input).is_ok()));
+    }
+}