update json tests

src/client.rs

@@ -827,7 +827,7 @@ mod tests {
         let mut json_data = HashMap::new();
         json_data.insert("foo", "bar");
 
-        r = r.json(&json_data);
+        r = r.json(&json_data).unwrap();
 
         // Make sure the content type was set
         assert_eq!(r.headers.get::<ContentType>(), Some(&ContentType::json()));
@@ -837,4 +837,24 @@ mod tests {
         let body_should_be = serde_json::to_string(&json_data).unwrap();
         assert_eq!(buf, body_should_be);
     }
+
+    #[test]
+    fn add_json_fail() {
+        use serde::{Serialize, Serializer};
+        use serde::ser::Error;
+        struct MyStruct;
+        impl Serialize for MyStruct {
+            fn serialize<S>(&self, _serializer: S) -> Result<S::Ok, S::Error>
+                where S: Serializer
+                {
+                    Err(S::Error::custom("nope"))
+                }
+        }
+
+        let client = Client::new().unwrap();
+        let some_url = "https://google.com/";
+        let r = client.post(some_url);
+        let json_data = MyStruct{};
+        assert_eq!(format!("{}", r.json(&json_data).unwrap_err()), "nope".to_string());
+    }
 }