fixed issue with tests. ES6 classes requires class vars to be established in the constructor

assets/js/WakaTime.js

@@ -6,13 +6,15 @@ import devtools from './libs/devtools-detect.js';
 
 class WakaTime {
 
-    detectionIntervalInSeconds = 60; //default
+    constructor(props) {
+        this.detectionIntervalInSeconds = 60; //default
 
-    loggingType = 'domain'; //default
+        this.loggingType = 'domain'; //default
 
-    heartbeatApiUrl = 'https://wakatime.com/api/v1/users/current/heartbeats';
+        this.heartbeatApiUrl = 'https://wakatime.com/api/v1/users/current/heartbeats';
 
-    currentUserApiUrl = 'https://wakatime.com/api/v1/users/current';
+        this.currentUserApiUrl = 'https://wakatime.com/api/v1/users/current';
+    }
 
     /**
      * Checks if the user is logged in.

assets/js/components/WakaTime.react.js

@@ -6,9 +6,11 @@ import changeExtensionIcon from '../helpers/changeExtensionIcon.js';
 import WakaTimeOriginal from '../WakaTime.js';
 
 class WakaTime extends React.Component {
-    logoutUserUrl = 'https://wakatime.com/logout';
 
-    state = {
+    constructor(props) {
+        super(props);
+        this.logoutUserUrl = 'https://wakatime.com/logout';
+        this.state = {
             user: {
                 full_name: null,
                 email: null,
@@ -16,7 +18,8 @@ class WakaTime extends React.Component {
             },
             loggedIn: false,
             loggingEnabled: false
-    };
+        }
+    }
 
     componentDidMount() {