Shouldn't mutate original data in res.end

index.js

@@ -104,10 +104,6 @@ const resolveRequestModelSchema = (req) => {
 };
 
 const sendData = (res, data, encoding) => {
-  // 'res.end' requires a Buffer or String so if it's not one, create a String
-  if (!(data instanceof Buffer) && !_.isString(data)) {
-    data = JSON.stringify(data);
-  }
   res.end(data, encoding);
 };
 
@@ -201,7 +197,7 @@ const validateResponse = (req, res, next) => {
         debug(`  Response validation errors: \n${util.inspect(validator.errors)}`);
         if (options.responseValidationFn) {
           options.responseValidationFn(req, val, validator.errors);
-          sendData(res, val, encoding);
+          sendData(res, data, encoding);
         } else {
           const err = {
             message: `Response schema validation failed for ${req.method}${req.originalUrl}`,
@@ -213,7 +209,7 @@ const validateResponse = (req, res, next) => {
         }
       } else {
         debug('Response validation success');
-        sendData(res, val, encoding);
+        sendData(res, data, encoding);
       }
     }
   };

test/pet-store.spec.js

@@ -269,6 +269,45 @@ describe('pet store', () => {
         })
         .end(done);
     });
+
+    it('should process valid string response', (done) => {
+      const router = Router();
+      router.get('/firstname/:username', (req, res) => {
+        res.json('firstname1');
+      });
+      const app = createServer(router, optsValidateAll);
+
+      request(app)
+        .get('/firstname/user1')
+        .expect(200)
+        .end(done);
+    });
+
+    it('fails with 500 response code due to invalid response string return', (done) => {
+      const router = Router();
+      router.get('/firstname/:username', (req, res) => {
+        res.json({});
+      });
+      const app = createServer(router, optsValidateAll);
+
+      request(app)
+        .get('/firstname/user1')
+        .expect(500)
+        .end(done);
+    });
+
+    it('should process valid boolean response', (done) => {
+      const router = Router();
+      router.get('/isValidUser/:username', (req, res) => {
+        res.json(false);
+      });
+      const app = createServer(router, optsValidateAll);
+
+      request(app)
+        .get('/isValidUser/user1')
+        .expect(200)
+        .end(done);
+    });
   });
 
   describe('supports overriding ajv settings', () => {

test/swagger-schemas/pet-store.json

@@ -1474,6 +1474,66 @@
           }
         }
       }
+    },
+    "/firstname/{username}": {
+      "get": {
+        "tags": [
+          "user"
+        ],
+        "summary": "Get user first name by user name",
+        "description": "",
+        "operationId": "getUserByName",
+        "produces": [
+          "application/json"
+        ],
+        "parameters": [
+          {
+            "name": "username",
+            "in": "path",
+            "description": "The name that needs to be fetched. Use user1 for testing. ",
+            "required": true,
+            "type": "string"
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "successful operation",
+            "schema": {
+              "type": "string"
+            }
+          }
+        }
+      }
+    },
+    "/isValidUser/{username}": {
+      "get": {
+        "tags": [
+          "user"
+        ],
+        "summary": "Checks if it is a valid username",
+        "description": "",
+        "operationId": "getUserByName",
+        "produces": [
+          "application/json"
+        ],
+        "parameters": [
+          {
+            "name": "username",
+            "in": "path",
+            "description": "The name that needs to be fetched. Use user1 for testing. ",
+            "required": true,
+            "type": "string"
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "successful operation",
+            "schema": {
+              "type": "boolean"
+            }
+          }
+        }
+      }
     }
   },
   "securityDefinitions": {