@nightwatch/nightwatch-inspector/src/background.js

Nightwatch Inspector that allows you to tests command directly from the browser

const connections = {};

chrome.runtime.onConnect.addListener(function (port) {
  const extensionListener = function (message, sender, sendResponse) {
    /** 
     * The original connection event doesn't include the tab ID of the DevTools page, 
     * so we need to send it explicitly.
     */
    if (message.action === 'INIT') {
      connections[message.tabId] = port;
      
      return;
    } 
    // Send all messages recieved from devtools to content js
    chrome.tabs.sendMessage(message.tabId, message, sendResponse);
  };
  
  // Listen to messages sent from the DevTools page
  port.onMessage.addListener(extensionListener);
  
  port.onDisconnect.addListener(function(port) {
    
    var tabs = Object.keys(connections);
    for (var i=0, len=tabs.length; i < len; i++) {
      
      if (connections[tabs[i]] === port) {
        chrome.tabs.sendMessage(Number(tabs[i]), {
          tabId: tabs[i],
          action: 'EXPLORE_MODE',
          content: false
        });
        delete connections[tabs[i]];
        break;
      }
    }
  });
});