chromeLauncher/Lighthouse: Mocking chained dependencies that return promises using Jest












0















I have an application that includes a Node script that runs Lighthouse v3 programatically and headlessly (Lighthouse documentation) to test the application's performance.



I wrote some Jest tests for this which pass locally. The tests are not testing Lighthouse itself, but rather how the Node script deals with with the results data returned from Lighthouse. Therefore, the Lighthouse dependency must be mocked.



In the course of doing my testing I have discovered that chrome-launcher, which is invoked by Lighthouse, launches when I'm doing my Jest test. This means I am not mocking this dependency correctly. I thought it was enough to mock Lighthouse and have done so but I am confused about how I can mock the 'thennable' chrome launcher function function.



The launchChromeAndRunLighthouse function below is from the Lighthouse Node documentation.



lighthouse.js



    const lighthouse = require('lighthouse'); 
const chromeLauncher = require('chrome-launcher');

function launchChromeAndRunLighthouse(url, opts, lConfig = null) {
return chromeLauncher
.launch({ chromeFlags: opts.chromeFlags })
.then(chrome => {
const options = { ...opts, port: chrome.port };
return lighthouse(url, options, lConfig).then(results =>
chrome.kill().then(() => results.lhr),
);
});
}

function myFunc(config) {
launchChromeAndRunLighthouse(myAppUrl, config);
// manipulates data returned from launchChromeAndRunLighthouse
return true;
}

module.exports = myFunc;


lighthouse.test.js



    import myFunc from './lighthouse';  

jest.mock('lighthouse', () =>
jest.fn().mockResolvedValue({
lhr: {
categories: {
performance: {
id: 'performance',
score: 1,
}
},
},
}),
);

// chromeLauncher actually gets invoked by this
describe('myfunc', () => {
it('tests myfunc', async () => {
const result = await myFunc(config);
expect(result).toEqual(true);
});
});


New to Jest and confused at how I can mock chromeLauncher so it's prevented from launching. Thanks










share|improve this question





























    0















    I have an application that includes a Node script that runs Lighthouse v3 programatically and headlessly (Lighthouse documentation) to test the application's performance.



    I wrote some Jest tests for this which pass locally. The tests are not testing Lighthouse itself, but rather how the Node script deals with with the results data returned from Lighthouse. Therefore, the Lighthouse dependency must be mocked.



    In the course of doing my testing I have discovered that chrome-launcher, which is invoked by Lighthouse, launches when I'm doing my Jest test. This means I am not mocking this dependency correctly. I thought it was enough to mock Lighthouse and have done so but I am confused about how I can mock the 'thennable' chrome launcher function function.



    The launchChromeAndRunLighthouse function below is from the Lighthouse Node documentation.



    lighthouse.js



        const lighthouse = require('lighthouse'); 
    const chromeLauncher = require('chrome-launcher');

    function launchChromeAndRunLighthouse(url, opts, lConfig = null) {
    return chromeLauncher
    .launch({ chromeFlags: opts.chromeFlags })
    .then(chrome => {
    const options = { ...opts, port: chrome.port };
    return lighthouse(url, options, lConfig).then(results =>
    chrome.kill().then(() => results.lhr),
    );
    });
    }

    function myFunc(config) {
    launchChromeAndRunLighthouse(myAppUrl, config);
    // manipulates data returned from launchChromeAndRunLighthouse
    return true;
    }

    module.exports = myFunc;


    lighthouse.test.js



        import myFunc from './lighthouse';  

    jest.mock('lighthouse', () =>
    jest.fn().mockResolvedValue({
    lhr: {
    categories: {
    performance: {
    id: 'performance',
    score: 1,
    }
    },
    },
    }),
    );

    // chromeLauncher actually gets invoked by this
    describe('myfunc', () => {
    it('tests myfunc', async () => {
    const result = await myFunc(config);
    expect(result).toEqual(true);
    });
    });


    New to Jest and confused at how I can mock chromeLauncher so it's prevented from launching. Thanks










    share|improve this question



























      0












      0








      0








      I have an application that includes a Node script that runs Lighthouse v3 programatically and headlessly (Lighthouse documentation) to test the application's performance.



      I wrote some Jest tests for this which pass locally. The tests are not testing Lighthouse itself, but rather how the Node script deals with with the results data returned from Lighthouse. Therefore, the Lighthouse dependency must be mocked.



      In the course of doing my testing I have discovered that chrome-launcher, which is invoked by Lighthouse, launches when I'm doing my Jest test. This means I am not mocking this dependency correctly. I thought it was enough to mock Lighthouse and have done so but I am confused about how I can mock the 'thennable' chrome launcher function function.



      The launchChromeAndRunLighthouse function below is from the Lighthouse Node documentation.



      lighthouse.js



          const lighthouse = require('lighthouse'); 
      const chromeLauncher = require('chrome-launcher');

      function launchChromeAndRunLighthouse(url, opts, lConfig = null) {
      return chromeLauncher
      .launch({ chromeFlags: opts.chromeFlags })
      .then(chrome => {
      const options = { ...opts, port: chrome.port };
      return lighthouse(url, options, lConfig).then(results =>
      chrome.kill().then(() => results.lhr),
      );
      });
      }

      function myFunc(config) {
      launchChromeAndRunLighthouse(myAppUrl, config);
      // manipulates data returned from launchChromeAndRunLighthouse
      return true;
      }

      module.exports = myFunc;


      lighthouse.test.js



          import myFunc from './lighthouse';  

      jest.mock('lighthouse', () =>
      jest.fn().mockResolvedValue({
      lhr: {
      categories: {
      performance: {
      id: 'performance',
      score: 1,
      }
      },
      },
      }),
      );

      // chromeLauncher actually gets invoked by this
      describe('myfunc', () => {
      it('tests myfunc', async () => {
      const result = await myFunc(config);
      expect(result).toEqual(true);
      });
      });


      New to Jest and confused at how I can mock chromeLauncher so it's prevented from launching. Thanks










      share|improve this question
















      I have an application that includes a Node script that runs Lighthouse v3 programatically and headlessly (Lighthouse documentation) to test the application's performance.



      I wrote some Jest tests for this which pass locally. The tests are not testing Lighthouse itself, but rather how the Node script deals with with the results data returned from Lighthouse. Therefore, the Lighthouse dependency must be mocked.



      In the course of doing my testing I have discovered that chrome-launcher, which is invoked by Lighthouse, launches when I'm doing my Jest test. This means I am not mocking this dependency correctly. I thought it was enough to mock Lighthouse and have done so but I am confused about how I can mock the 'thennable' chrome launcher function function.



      The launchChromeAndRunLighthouse function below is from the Lighthouse Node documentation.



      lighthouse.js



          const lighthouse = require('lighthouse'); 
      const chromeLauncher = require('chrome-launcher');

      function launchChromeAndRunLighthouse(url, opts, lConfig = null) {
      return chromeLauncher
      .launch({ chromeFlags: opts.chromeFlags })
      .then(chrome => {
      const options = { ...opts, port: chrome.port };
      return lighthouse(url, options, lConfig).then(results =>
      chrome.kill().then(() => results.lhr),
      );
      });
      }

      function myFunc(config) {
      launchChromeAndRunLighthouse(myAppUrl, config);
      // manipulates data returned from launchChromeAndRunLighthouse
      return true;
      }

      module.exports = myFunc;


      lighthouse.test.js



          import myFunc from './lighthouse';  

      jest.mock('lighthouse', () =>
      jest.fn().mockResolvedValue({
      lhr: {
      categories: {
      performance: {
      id: 'performance',
      score: 1,
      }
      },
      },
      }),
      );

      // chromeLauncher actually gets invoked by this
      describe('myfunc', () => {
      it('tests myfunc', async () => {
      const result = await myFunc(config);
      expect(result).toEqual(true);
      });
      });


      New to Jest and confused at how I can mock chromeLauncher so it's prevented from launching. Thanks







      node.js unit-testing jestjs lighthouse






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Nov 19 '18 at 7:46









      skyboyer

      3,66111129




      3,66111129










      asked Nov 18 '18 at 20:01









      BenjaminBenjamin

      11729




      11729
























          0






          active

          oldest

          votes











          Your Answer






          StackExchange.ifUsing("editor", function () {
          StackExchange.using("externalEditor", function () {
          StackExchange.using("snippets", function () {
          StackExchange.snippets.init();
          });
          });
          }, "code-snippets");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "1"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53364894%2fchromelauncher-lighthouse-mocking-chained-dependencies-that-return-promises-usi%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          0






          active

          oldest

          votes








          0






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes
















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Stack Overflow!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53364894%2fchromelauncher-lighthouse-mocking-chained-dependencies-that-return-promises-usi%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          這個網誌中的熱門文章

          Xamarin.form Move up view when keyboard appear

          Post-Redirect-Get with Spring WebFlux and Thymeleaf

          Anylogic : not able to use stopDelay()