explanation for tests in sorted_json

Author: EtomicBomb

src/librustdoc/html/render/sorted_json/tests.rs

@@ -17,6 +17,8 @@ fn check(json: SortedJson, serialized: &str) {
     assert_eq!(serde_json::to_string(&json).unwrap(), serialized);
 }
 
+// Test this basic are needed because we are testing that our Display impl + serialize impl don't
+// nest everything in extra level of string. We also are testing round trip.
 #[test]
 fn escape_json_number() {
     let json = SortedJson::serialize(3);