Headless Chrome times out without executing any tests

Explanation of the problem

When attempting to configure headless Chrome in a project and executing tests on an OSX machine, the test runner successfully runs all tests on headless Chrome. However, when attempting to run the same tests on a Linux server, the tests connect to the socket, then disconnect and display an error message stating “Karma tests failed.” The error message specifically indicates that the HeadlessChrome running on Linux is disconnected due to no message in 120000ms. The configuration file includes the necessary dependencies such as karma-jasmine and karma-chrome-launcher, and uses custom launchers to launch the ChromeHeadless with the necessary flags. Attempts were made to use suggested flags like “–no-sandbox” and “–disable-web-security”, but the issue persisted. It is unclear why the tests are not executing correctly on the Linux server.

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Problem solution for Headless Chrome times out without executing any tests

npm install
npm rebuild
npm test

const process = require('process');
process.env.CHROME_BIN = require('puppeteer').executablePath();

Other popular problems with Karma

//example of karma.conf.js
module.exports = function(config) {
  config.set({
    files: [
      'src/**/*.js', //this is the pattern for source files
      'test/**/*.spec.js' //this is the pattern for test files
    ],
    frameworks: ['jasmine'],
    preprocessors: {
      'src/**/*.js': ['babel'],
      'test/**/*.spec.js': ['babel']
    },
    //...
  });
};

Problem: Tests are failing with a timeout

Another common problem with Karma is that tests are failing with a timeout error. This can happen when tests are taking too long to complete or when there is a problem with the test runner’s communication with the browser.

Solution:

To solve this problem, you can increase the timeout value in the Karma configuration file or you can fix the problem by looking into the browser’s console for error messages and fix them.

//example of karma.conf.js
module.exports = function(config) {
  config.set({
    //...
    browserNoActivityTimeout: 60000, //increase the timeout value to 60 seconds
    //...
  });
};

Problem: Tests are failing with a “Cannot read property ‘xxx’ of undefined” error

Another common problem with Karma is that tests are failing with a “Cannot read property ‘xxx’ of undefined” error. This error happens when the test is trying to access a property of an object that is undefined. This can happen when an object is not defined or when a module is not imported correctly.

Solution:

To solve this problem, you should check that all the required modules are imported correctly and that objects are defined before they are used in the test.

//example of test file
import { MyObject } from './myObject';

describe('MyObject', () => {
  it('should have a property x', () => {
    const obj = new MyObject();
    expect(obj.x).toBeDefined();
  });
});

//example of myObject.js
export class MyObject {
  constructor() {
    this.x = 'some value';
  }
}

A brief introduction to Karma

Karma is a test runner for JavaScript that can be used to run tests for web applications. It is designed to work with a variety of testing frameworks, such as Jasmine, Mocha, and Protractor. Karma uses a browser-based test runner to execute tests, which allows you to run tests in multiple browsers and on different platforms. This allows you to test your web application in a variety of environments and ensure that it works as expected.

Karma is highly configurable and can be integrated with a variety of build tools, such as Grunt, Gulp, and Webpack. It also has a plugin system that allows you to add additional functionality, such as code coverage reporting, test reporting, and test watch mode. Karma also provides an API that allows you to interact with the test runner programmatically, which can be useful for automating testing tasks. Overall, Karma is a powerful tool that can help you test your web application and ensure that it is working correctly.

Most popular use cases for Karma

describe('MyFunction', () => {
  it('should return the correct value', () => {
    expect(MyFunction()).toEqual('some value');
  });
});