Fix Broken chrono Example (#126)

* Add quickcheck as test dependencie

* Use timestamp nanos

* Add test property for en/decoding

* Fix existing test

* Remove quickcheck dependency

* Normalize `DateTime` values in claims

examples/custom_chrono.rs

@@ -13,6 +13,19 @@ struct Claims {
     exp: DateTime<Utc>,
 }
 
+impl Claims {
+    /// If a token should always be equal to its representation after serializing and deserializing
+    /// again, this function must be used for construction. `DateTime` contains a microsecond field
+    /// but JWT timestamps are defined as UNIX timestamps (seconds). This function normalizes the
+    /// timestamps.
+    pub fn new(sub: String, iat: DateTime<Utc>, exp: DateTime<Utc>) -> Self {
+        // normalize the timestamps by stripping of microseconds
+        let iat = iat.date().and_hms_milli(iat.hour(), iat.minute(), iat.second(), 0);
+        let exp = exp.date().and_hms_milli(exp.hour(), exp.minute(), exp.second(), 0);
+        Self { sub, iat, exp }
+    }
+}
+
 mod jwt_numeric_date {
     //! Custom serialization of DateTime<Utc> to conform with the JWT spec (RFC 7519 section 2, "Numeric Date")
     use chrono::{DateTime, TimeZone, Utc};
@@ -42,6 +55,8 @@ mod jwt_numeric_date {
         const EXPECTED_TOKEN: &str = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJDdXN0b20gRGF0ZVRpbWUgc2VyL2RlIiwiaWF0IjowLCJleHAiOjMyNTAzNjgwMDAwfQ.RTgha0S53MjPC2pMA4e2oMzaBxSY3DMjiYR2qFfV55A";
 
         use super::super::{Claims, SECRET};
+        use chrono::{Duration, TimeZone, Utc};
+        use jsonwebtoken::{decode, encode, DecodingKey, EncodingKey, Header, Validation};
 
         #[test]
         fn round_trip() {
@@ -49,7 +64,7 @@ mod jwt_numeric_date {
             let iat = Utc.timestamp(0, 0);
             let exp = Utc.timestamp(32503680000, 0);
 
-            let claims = Claims { sub: sub.clone(), iat, exp };
+            let claims = Claims::new(sub.clone(), iat, exp);
 
             let token =
                 encode(&Header::default(), &claims, &EncodingKey::from_secret(SECRET.as_ref()))
@@ -72,11 +87,37 @@ mod jwt_numeric_date {
             // A token with the expiry of i64::MAX + 1
             let overflow_token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJDdXN0b20gRGF0ZVRpbWUgc2VyL2RlIiwiaWF0IjowLCJleHAiOjkyMjMzNzIwMzY4NTQ3NzYwMDB9.G2PKreA27U8_xOwuIeCYXacFYeR46f9FyENIZfCrvEc";
 
-            let decode_result =
-                decode::<Claims>(&overflow_token, SECRET.as_ref(), &Validation::default());
+            let decode_result = decode::<Claims>(
+                &overflow_token,
+                &DecodingKey::from_secret(SECRET.as_ref()),
+                &Validation::default(),
+            );
 
             assert!(decode_result.is_err());
         }
+
+        #[test]
+        fn to_token_and_parse_equals_identity() {
+            let iat = Utc::now();
+            let exp = iat + Duration::days(1);
+            let sub = "Custom DateTime ser/de".to_string();
+
+            let claims = Claims::new(sub.clone(), iat, exp);
+
+            let token =
+                encode(&Header::default(), &claims, &EncodingKey::from_secret(SECRET.as_ref()))
+                    .expect("Failed to encode claims");
+
+            let decoded = decode::<Claims>(
+                &token,
+                &DecodingKey::from_secret(SECRET.as_ref()),
+                &Validation::default(),
+            )
+            .expect("Failed to decode token")
+            .claims;
+
+            assert_eq!(claims, decoded);
+        }
     }
 }
 
@@ -85,7 +126,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let iat = Utc::now();
     let exp = iat + chrono::Duration::days(1);
 
-    let claims = Claims { sub: sub.clone(), iat, exp };
+    let claims = Claims::new(sub.clone(), iat, exp);
 
     let token = jsonwebtoken::encode(
         &Header::default(),