Start making representation work

tests/json_parser.rs

@@ -3,6 +3,7 @@ use parser_combinator::combinators::repeated;
 use parser_combinator::primitives::{any_char, literal, literal_char, one_of, pred};
 use parser_combinator::sequence::seq;
 use parser_combinator::Parser;
+use parser_combinator::Representation;
 
 use proptest::prelude::*;
 
@@ -53,6 +54,7 @@ impl<'a, T, P> JsonParser<'a, T> for P where P: Parser<&'a str, T, &'a str> {}
 fn json_null<'a>() -> impl JsonParser<'a, JsonValue> {
     literal("null").to(JsonValue::Null)
 }
+
 fn json_bool<'a>() -> impl JsonParser<'a, JsonValue> {
     choice((
         literal("true").to(JsonValue::Bool(true)),
@@ -234,3 +236,8 @@ fn parse_json_document() {
     let parsed_json = json_object().parse(test_json);
     assert!(parsed_json.is_ok());
 }
+
+#[test]
+fn test_representations() {
+    assert_eq!(json_null().representation(), Representation::new("null"));
+}