diff --git a/lib/stubber.dart b/lib/stubber.dart
index 2b8164f..323afc7 100644
--- a/lib/stubber.dart
+++ b/lib/stubber.dart
@@ -1,10 +1,15 @@
 import 'dart:collection';
 import 'dart:io';
-import 'package:flutter_gherkin_addons/flutter_gherkin_addons.dart';
+
 import 'package:mock_web_server/mock_web_server.dart';
 
 class Stubber {
+  Future<void> Function(HttpRequest request) onMissingStub;
+
+  Stubber({this.onMissingStub});
+
   MockWebServer _mockWebServer = MockWebServer(port: 8081);
+
   HashMap<String, Stub> stubs = HashMap();
   start() async {
     await _mockWebServer.start();
@@ -26,18 +31,24 @@ class Stubber {
   Future<MockResponse> _dispatcher(HttpRequest request) async {
     if (stubs.containsKey(_requestToKey(request))) {
       var _stub = stubs[_requestToKey(request)];
-      var _response=_stub._responseBuilder(request);
+      var _response = _stub._responseBuilder(request);
       return MockResponse()
         ..httpCode = _response._statusCode
         ..body = _response._body
         ..headers = _response.headers;
+    } else {
+      if (onMissingStub != null) {
+        await onMissingStub(request);
+      }
     }
     return _defaultAnswer;
   }
 
   get _defaultAnswer => MockResponse()..httpCode = 404;
 }
+
 typedef Response ResponseBuilder(HttpRequest request);
+
 class Stub {
   final String url;
   final String method;
@@ -56,39 +67,51 @@ class Response {
 
   Response(this._statusCode, this._body, {this.headers});
 }
+
 class StubFor {
-  static Stub staticHttpGet(String url, Response response){
+  static Stub staticHttpGet(String url, Response response) {
     return _staticStub("GET", url, response);
   }
-  static Stub staticHttpPost(String url, Response response){
+
+  static Stub staticHttpPost(String url, Response response) {
     return _staticStub("POST", url, response);
   }
-  static Stub staticHttpPut(String url, Response response){
+
+  static Stub staticHttpPut(String url, Response response) {
     return _staticStub("PUT", url, response);
   }
-  static Stub staticHttpPatch(String url, Response response){
+
+  static Stub staticHttpPatch(String url, Response response) {
     return _staticStub("PATCH", url, response);
   }
-  static Stub staticHttpDelete(String url, Response response){
+
+  static Stub staticHttpDelete(String url, Response response) {
     return _staticStub("DELETE", url, response);
   }
-  static Stub _staticStub(String method, String url, Response response){
-    return Stub(method, url, (request) {return response;});
+
+  static Stub _staticStub(String method, String url, Response response) {
+    return Stub(method, url, (request) {
+      return response;
+    });
   }
-  static Stub httpGet(String url, ResponseBuilder responseBuilder){
+
+  static Stub httpGet(String url, ResponseBuilder responseBuilder) {
     return Stub("GET", url, responseBuilder);
   }
-  static Stub httpPost(String url, ResponseBuilder responseBuilder){
+
+  static Stub httpPost(String url, ResponseBuilder responseBuilder) {
     return Stub("POST", url, responseBuilder);
   }
-  static Stub httpPut(String url, ResponseBuilder responseBuilder){
+
+  static Stub httpPut(String url, ResponseBuilder responseBuilder) {
     return Stub("PUT", url, responseBuilder);
   }
-  static Stub httpPatch(String url, ResponseBuilder responseBuilder){
+
+  static Stub httpPatch(String url, ResponseBuilder responseBuilder) {
     return Stub("PATCH", url, responseBuilder);
   }
-  static Stub httpDelete(String url, ResponseBuilder responseBuilder){
+
+  static Stub httpDelete(String url, ResponseBuilder responseBuilder) {
     return Stub("DELETE", url, responseBuilder);
   }
-
-}
\ No newline at end of file
+}
diff --git a/lib/wrapper.dart b/lib/wrapper.dart
index c8c5fcf..fa69d8b 100644
--- a/lib/wrapper.dart
+++ b/lib/wrapper.dart
@@ -1,40 +1,44 @@
 import 'dart:io';
+import 'dart:io' show Platform;
+
+import 'package:flutter_driver/flutter_driver.dart';
+import 'package:flutter_gherkin/flutter_gherkin.dart';
 import 'package:flutter_gherkin_addons/stubber.dart';
 import 'package:gherkin/gherkin.dart';
-import 'package:flutter_gherkin/flutter_gherkin.dart';
 import 'package:glob/glob.dart';
-import 'package:flutter_driver/flutter_driver.dart';
 import "package:path/path.dart" show dirname;
-import 'dart:io' show Platform;
-
 import 'package:yaml/yaml.dart';
 
 class TestRuntime {
   static Stubber _stubber;
-  static addStub(Stub stub){
+
+  static Future<void> Function(HttpRequest request) onMissingStub;
+
+  static addStub(Stub stub) {
     _stubber.stub(stub);
   }
-  static Future<void> start(Iterable<StepDefinitionBase> steps,[Iterable<Hook> hooks]) async {
+
+  static Future<void> start(Iterable<StepDefinitionBase> steps,
+      [Iterable<Hook> hooks]) async {
     String path = dirname(Platform.script.toString());
     int index = path.indexOf("test_driver");
     String dir = path.substring(index);
     Map mapConfig = loadYaml(new File("$dir/config.yaml").readAsStringSync());
-    List<Hook> arrHooks=[];
-    if(hooks!=null){
+    List<Hook> arrHooks = [];
+    if (hooks != null) {
       arrHooks.addAll(hooks);
     }
-    if(mapConfig['screenshots']!=null && mapConfig['screenshots']){
+    if (mapConfig['screenshots'] != null && mapConfig['screenshots']) {
       arrHooks.add(AttachScreenshotOnFailedStepHook());
     }
-    var reporters=mapConfig['reporting']!=null && mapConfig['reporting']?[
-      ProgressReporter(),
-      TestRunSummaryReporter(),
-      JsonReporter(path: testOutputsDirectory + '/report.json')
-    ]:[
-      ProgressReporter(),
-      TestRunSummaryReporter()
-    ];
-    _stubber = Stubber();
+    var reporters = mapConfig['reporting'] != null && mapConfig['reporting']
+        ? [
+            ProgressReporter(),
+            TestRunSummaryReporter(),
+            JsonReporter(path: testOutputsDirectory + '/report.json')
+          ]
+        : [ProgressReporter(), TestRunSummaryReporter()];
+    _stubber = Stubber(onMissingStub: onMissingStub);
     var config = FlutterTestConfiguration()
       ..features = [Glob("$dir/features/**.feature")]
       ..hooks = arrHooks
@@ -43,7 +47,7 @@ class TestRuntime {
       ..restartAppBetweenScenarios = true
       ..targetAppPath = "$dir/app.dart"
       ..exitAfterTestRun = true;
-    if(mapConfig['stubbing']!=null && mapConfig['stubbing']) {
+    if (mapConfig['stubbing'] != null && mapConfig['stubbing']) {
       await _stubber.start();
       await GherkinRunner().execute(config);
       return await _stubber.stop();