diff --git a/README.md b/README.md
index 7bdb087..335c9cd 100644
--- a/README.md
+++ b/README.md
@@ -2,13 +2,10 @@
 
 A webrtc interface wrapped in dart language.
 
-
 Use the [dart/js](https://pub.dev/packages/js) library to re-wrap the [webrtc](https://developer.mozilla.org/en-US/docs/Web/API/WebRTC_API) js interface of the browser, to adapted common browsers.
 
 This library will be used for [flutter-webrtc](https://github.com/flutter-webrtc/flutter-webrtc) for [flutter web](https://flutter.dev/web) plugin.
 
-
-
 ## How to develop
 
 * `git clone https://github.com/flutter-webrtc/dart-webrtc && cd dart-webrtc`
diff --git a/lib/src/media_devices.dart b/lib/src/media_devices.dart
index 661f56e..8d96508 100644
--- a/lib/src/media_devices.dart
+++ b/lib/src/media_devices.dart
@@ -1,6 +1,4 @@
-import 'package:webrtc_interface/webrtc_interface.dart';
 import '../dart_webrtc.dart';
-import 'factory_impl.dart';
 
 class MediaDevices {
   @Deprecated(
diff --git a/lib/src/media_recorder.dart b/lib/src/media_recorder.dart
index 0fc6f84..7d3412c 100644
--- a/lib/src/media_recorder.dart
+++ b/lib/src/media_recorder.dart
@@ -1,8 +1,6 @@
 import 'package:webrtc_interface/src/media_recorder.dart' as _interface;
-import 'package:webrtc_interface/webrtc_interface.dart';
 
 import '../dart_webrtc.dart';
-import 'factory_impl.dart';
 
 class MediaRecorder extends _interface.MediaRecorder {
   MediaRecorder() : _delegate = mediaRecorder();
diff --git a/lib/src/mediadevices_impl.dart b/lib/src/mediadevices_impl.dart
index b4079ac..4b7fa4e 100644
--- a/lib/src/mediadevices_impl.dart
+++ b/lib/src/mediadevices_impl.dart
@@ -1,6 +1,5 @@
 import 'dart:async';
 import 'dart:html' as html;
-import 'dart:html_common';
 import 'dart:js' as js;
 import 'dart:js_util' as jsutil;
 import 'package:webrtc_interface/webrtc_interface.dart';
diff --git a/web/p2p/p2p.dart b/web/p2p/p2p.dart
index 819337e..a3f5ec7 100644
--- a/web/p2p/p2p.dart
+++ b/web/p2p/p2p.dart
@@ -1,8 +1,8 @@
 import 'dart:html' as html;
-import 'package:test/test.dart';
 
 import 'package:dart_webrtc/dart_webrtc.dart';
 import 'package:js/js.dart';
+import 'package:test/test.dart';
 
 import 'signaling.dart';
 
diff --git a/web/test_media_stream.dart b/web/test_media_stream.dart
index ce531fd..cd82314 100644
--- a/web/test_media_stream.dart
+++ b/web/test_media_stream.dart
@@ -1,44 +1,44 @@
 import 'package:dart_webrtc/dart_webrtc.dart';
 import 'package:test/test.dart';
 
-late MediaStream mediaStream;
+MediaStream? mediaStream;
 
 List<void Function()> testFunctions = <void Function()>[
-  () => test('MediaStream.constructor()', () async {
+  () => test('mediaStream?.constructor()', () async {
         mediaStream = await navigator.mediaDevices
             .getUserMedia({'audio': true, 'video': true});
 
-        expect(mediaStream.id != null, true);
+        expect(mediaStream?.id != null, true);
       }),
-  () => test('MediaStream.active()', () {
-        expect(mediaStream.active, true);
+  () => test('mediaStream?.active()', () {
+        expect(mediaStream?.active, true);
       }),
-  () => test('MediaStream.getTracks()', () {
-        expect(mediaStream.getTracks().length, 2);
+  () => test('mediaStream?.getTracks()', () {
+        expect(mediaStream?.getTracks().length, 2);
       }),
-  () => test('MediaStream.getAudioTracks()', () {
-        expect(mediaStream.getAudioTracks().length, 1);
-        var track =
-            mediaStream.getTrackById(mediaStream.getAudioTracks()[0].id!);
-        expect(track?.id, mediaStream.getAudioTracks()[0].id);
+  () => test('mediaStream?.getAudioTracks()', () {
+        expect(mediaStream?.getAudioTracks().length, 1);
+        var track = mediaStream
+            ?.getTrackById(mediaStream?.getAudioTracks()[0].id ?? '');
+        expect(track?.id, mediaStream?.getAudioTracks()[0].id);
       }),
-  () => test('MediaStream.getVideoTracks()', () {
-        expect(mediaStream.getVideoTracks().length, 1);
-        var track =
-            mediaStream.getTrackById(mediaStream.getVideoTracks()[0].id!);
-        expect(track!.id, mediaStream.getVideoTracks()[0].id);
+  () => test('mediaStream?.getVideoTracks()', () {
+        expect(mediaStream?.getVideoTracks().length, 1);
+        var track = mediaStream
+            ?.getTrackById(mediaStream?.getVideoTracks()[0].id ?? '');
+        expect(track!.id, mediaStream?.getVideoTracks()[0].id);
       }),
-  () => test('MediaStream.removeTrack()', () {
-        var track =
-            mediaStream.getTrackById(mediaStream.getVideoTracks()[0].id!);
-        mediaStream.removeTrack(track!);
-        expect(mediaStream.getVideoTracks().length, 0);
+  () => test('mediaStream?.removeTrack()', () {
+        var track = mediaStream
+            ?.getTrackById(mediaStream?.getVideoTracks()[0].id ?? '');
+        mediaStream?.removeTrack(track!);
+        expect(mediaStream?.getVideoTracks().length, 0);
       }),
-  () => test('MediaStream.close()', () {
-        mediaStream.getTracks().forEach((element) {
+  () => test('mediaStream?.close()', () {
+        mediaStream?.getTracks().forEach((element) {
           element.stop();
-          mediaStream.removeTrack(element);
+          mediaStream?.removeTrack(element);
         });
-        expect(mediaStream.getTracks().isEmpty, true);
+        expect(mediaStream?.getTracks().isEmpty, true);
       })
 ];
diff --git a/web/test_media_stream_track.dart b/web/test_media_stream_track.dart
index 45dce25..98ff06d 100644
--- a/web/test_media_stream_track.dart
+++ b/web/test_media_stream_track.dart
@@ -1,9 +1,7 @@
-import 'dart:html';
-
 import 'package:dart_webrtc/dart_webrtc.dart';
 import 'package:test/test.dart';
 
-late MediaStreamTrack audioTrack, videoTrack;
+MediaStreamTrack? audioTrack, videoTrack;
 
 List<void Function()> testFunctions = <void Function()>[
   () => test('MediaStreamTrack.constructor()', () async {
@@ -13,43 +11,43 @@ List<void Function()> testFunctions = <void Function()>[
         audioTrack = stream.getAudioTracks()[0];
         expect(audioTrack != null, true);
 
-        expect(audioTrack.kind, 'audio');
+        expect(audioTrack?.kind, 'audio');
 
         videoTrack = stream.getVideoTracks()[0];
         expect(videoTrack != null, true);
 
-        expect(videoTrack.kind, 'video');
+        expect(videoTrack?.kind, 'video');
       }),
   () => test('MediaStreamTrack.id()', () {
-        expect(audioTrack.id is String, true);
-        expect(audioTrack.id?.isNotEmpty, true);
-        expect(videoTrack.id is String, true);
-        expect(videoTrack.id?.isNotEmpty, true);
+        expect(audioTrack?.id is String, true);
+        expect(audioTrack?.id?.isNotEmpty, true);
+        expect(videoTrack?.id is String, true);
+        expect(videoTrack?.id?.isNotEmpty, true);
       }),
   () => test('MediaStreamTrack.label()', () {
-        expect(audioTrack.label is String, true);
-        expect(audioTrack.id?.isNotEmpty, true);
-        expect(videoTrack.id is String, true);
-        expect(videoTrack.id?.isNotEmpty, true);
+        expect(audioTrack?.label is String, true);
+        expect(audioTrack?.id?.isNotEmpty, true);
+        expect(videoTrack?.id is String, true);
+        expect(videoTrack?.id?.isNotEmpty, true);
       }),
   () => test('MediaStreamTrack.enabled()', () {
-        expect(audioTrack.enabled, true);
-        audioTrack.enabled = false;
-        expect(audioTrack.enabled, false);
+        expect(audioTrack?.enabled, true);
+        audioTrack?.enabled = false;
+        expect(audioTrack?.enabled, false);
 
-        expect(videoTrack.enabled, true);
-        videoTrack.enabled = false;
-        expect(videoTrack.enabled, false);
+        expect(videoTrack?.enabled, true);
+        videoTrack?.enabled = false;
+        expect(videoTrack?.enabled, false);
       }),
   () => test('MediaStreamTrack.readyState() | MediaStreamTrack.stop()', () {
         /*
-        expect(audioTrack.readyState, 'live');
-        audioTrack.stop();
-        expect(audioTrack.readyState, 'ended');
+        expect(audioTrack?.readyState, 'live');
+        audioTrack?.stop();
+        expect(audioTrack?.readyState, 'ended');
 
-        expect(videoTrack.readyState, 'live');
-        videoTrack.stop();
-        expect(videoTrack.readyState, 'ended');
+        expect(videoTrack?.readyState, 'live');
+        videoTrack?.stop();
+        expect(videoTrack?.readyState, 'ended');
         */
       })
 ];
diff --git a/web/test_video_element.dart b/web/test_video_element.dart
index 52d0b21..918dd52 100644
--- a/web/test_video_element.dart
+++ b/web/test_video_element.dart
@@ -1,7 +1,7 @@
 import 'package:dart_webrtc/dart_webrtc.dart';
 import 'package:test/test.dart';
 
-late RTCVideoElement localVideo;
+late RTCVideoElement? localVideo;
 
 List<void Function()> testFunctions = <void Function()>[
   () => test('RTCVideoElement.constructor()', () {
@@ -9,21 +9,21 @@ List<void Function()> testFunctions = <void Function()>[
         expect(localVideo != null, true);
       }),
   () => test('RTCVideoElement.muted()', () {
-        localVideo.muted = true;
-        expect(localVideo.muted, true);
-        localVideo.muted = false;
-        expect(localVideo.muted, false);
+        localVideo?.muted = true;
+        expect(localVideo?.muted, true);
+        localVideo?.muted = false;
+        expect(localVideo?.muted, false);
       }),
   () => test('RTCVideoElement.controls()', () {
-        localVideo.controls = false;
-        expect(localVideo.controls, false);
-        localVideo.controls = true;
-        expect(localVideo.controls, true);
+        localVideo?.controls = false;
+        expect(localVideo?.controls, false);
+        localVideo?.controls = true;
+        expect(localVideo?.controls, true);
       }),
   () => test('RTCVideoElement.autoplay()', () {
-        localVideo.autoplay = false;
-        expect(localVideo.autoplay, false);
-        localVideo.autoplay = true;
-        expect(localVideo.autoplay, true);
+        localVideo?.autoplay = false;
+        expect(localVideo?.autoplay, false);
+        localVideo?.autoplay = true;
+        expect(localVideo?.autoplay, true);
       })
 ];