test: add roundtrip::json_value

Adds a roundtrip helper for going to/from a json value. This can have
slightly different semantics in comparison to/from a json string.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

test/test-helpers/src/roundtrip.rs

@@ -20,6 +20,16 @@ where
     )
 }
 
+pub fn json_value<A>(a: A)
+where
+    for<'de> A: Clone + Debug + PartialEq + serde::Serialize + serde::Deserialize<'de>,
+{
+    assert_eq!(
+        a.clone(),
+        serde_json::from_value(serde_json::to_value(a).unwrap()).unwrap()
+    )
+}
+
 pub fn cbor<A>(a: A)
 where
     for<'de> A: Debug + PartialEq + minicbor::Encode + minicbor::Decode<'de>,