Correctly set json based Content-Type based on produces or consumes defined in swagger

lib/specValidator.js

@@ -555,6 +555,10 @@ class SpecValidator {
       }
     }
 
+    if (!(options.headers['content-type'] || options.headers['Content-Type'])) {
+      options.headers['Content-Type'] = utils.getJsonContentType(operation.consumes);
+    }
+
     let request = null;
     let validationResult = {};
     if (!foundIssues) {
@@ -687,7 +691,7 @@ class SpecValidator {
       }
       //ensure content-type header is present
       if (!(exampleResponseHeaders['content-type'] || exampleResponseHeaders['Content-Type'])) {
-        exampleResponseHeaders['content-type'] = operation.produces[0];
+        exampleResponseHeaders['content-type'] = utils.getJsonContentType(operation.produces);
       }
       let exampleResponse = new ResponseWrapper(exampleResponseStatusCode, exampleResponseBody, exampleResponseHeaders);
       let validationResult = self.validateResponse(operation, exampleResponse);

lib/util/utils.js

@@ -360,4 +360,21 @@ exports.removeObject = function removeObject(doc, ptr) {
     log.error(err);
   }
   return result;
-};
+};
+
+/*
+ * Finds the first content-type that contains "/json". Only supported Content-Types are 
+ * "text/json" & "application/json" so we perform first best match that contains '/json'
+ * @param {Array} Array of content-types.
+ * 
+ * @param {string} content-type that contains "/json".
+ */
+exports.getJsonContentType = function getJsonContentType(consumesOrProduces) {
+  var firstMatchedJson = null;
+  if (consumesOrProduces) {
+    firstMatchedJson = consumesOrProduces.find((contentType) => {
+      return (contentType.match(/.*\/json.*/ig) !== null);
+    });
+  }
+  return firstMatchedJson;
+};