Question 53538 in Javascript Question posted in
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How can add wait in cy.task() functions like validateZipFile and getZipFileSize in the cypress.config.js – Javascript

How can add wait in following cy.task() functions like validateZipFile and getZipFileSize in the in the cypress.config.js file ?

test.spec.js

cy.get('button[type="submit"]').contains("Download").click({force:true});
helperFunctions.validateZip("Booking Results Resource Pack - Task");

// helperFunctions.js

validateZip (text) {
    const dfilename = text.replace(/-|_|s/g,"");
    const downloadedFilename = dfilename+"ZipFile.zip";
   
    cy.task('getZipFileSize', downloadedFilename)
    .should('eq', 6149237)

    cy.task('validateZipFile', downloadedFilename)
    .should('deep.eq', [
      '__Booking-Resource__Question-Cards__Booking_BW.pdf', 
      '__Booking-Resource__Question-Cards__Booking-Colour.pdf'
    ]);
    
  }

cypress.config.js

    const AdmZip = require("adm-zip");
    
    const { defineConfig } = require('cypress')
    
    module.exports = defineConfig({
       e2e: {
        setupNodeEvents(on, config) {
          .....
    
    
            on('task', {
            validateZipFile: filename => {
              const downloadsFolder = config.downloadsFolder
              return  validateZipFile(path.join(downloadsFolder, filename))
            },
            getZipFileSize: filename => {
              const downloadsFolder = config.downloadsFolder
              const stats = fs.statSync(path.join(downloadsFolder, filename))
              return stats.size
            }
          });
    
          return config;
        },
        baseUrl: "https://staging-qa.someurl.com/",
        specPattern: "cypress/e2e/**/*.spec.{js,jsx,ts,tsx}",
      },
    })

 function validateZipFile(filename) {
  const zip = new AdmZip(filename)
  const zipEntries = zip.getEntries()
  const names = zipEntries.map(entry => entry.entryName).sort()
  return names
}
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2

Answers


  1. 0

    Assuming there is nothing on the web page to indicate the download has finished:

    There is this article by Yevhen Laichenkov from Kiev, Cypress: How to verify that file is downloaded with cy-verify-downloads.

    He mentions the memory issues with large files and cy.readFile(), has built a library cy-verify-downloads.

    cypress.config.js

    const { verifyDownloadTasks } = require('cy-verify-downloads');

module.exports = defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', verifyDownloadTasks);
    },
  },
})

    helper

    require('cy-verify-downloads').addCustomCommand()

validateZip (text) {
    const dfilename = text.replace(/-|_|s/g,"");
    const downloadedFilename = dfilename+"ZipFile.zip";
   
    cy.verifyDownload(downloadedFilename );

    cy.task('getZipFileSize', downloadedFilename)
      .should('eq', 6149237)

    cy.task('validateZipFile', downloadedFilename)
      .should('deep.eq', [
        '__Booking-Resource__Question-Cards__Booking_BW.pdf', 
        '__Booking-Resource__Question-Cards__Booking-Colour.pdf'
      ]);
  }

    Test (no change)

    cy.get('button[type="submit"]').contains("Download").click({force:true});
helperFunctions.validateZip("Booking Results Resource Pack - Task");

    Polling for the download

    You can build a task based on poll nodejs library.

    This method allows you to

    • configure timeout from the test
    • return true/false from the task and use the result in a should
    const fs = require('fs')
const poll = require('poll')

module.exports = defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', {

        poll: async ({filename, timeout = 30_000}) => {
          const {poll} = await import('poll')

          const filepath = path.resolve(config.downloadsFolder, filename)
          let fileExists = false;
          let stopPolling = false
          setTimeout(() => stopPolling = true, timeout)

          return new Promise(resolve => {
            const shouldStopPolling = () => {
              if (stopPolling) resolve(false)
              return stopPolling || fileExists
            }
            poll(
              () => { 
                fileExists = fs.existsSync(filepath) 
                if (fileExists) resolve(true)
              }, 
              100,                                   // check every 100ms
              shouldStopPolling
            )
          })
        },
      });
    },
  },
})

    Test

    cy.get('button[type="submit"]').contains("Download").click({force:true});

cy.task('poll', {filename, timeout: 30_000})
  .should('eq' true)

helperFunctions.validateZip("Booking Results Resource Pack - Task");

    Testing the poll task

    To check the above task I added a dummy file test1.pdf to downloads, then ran a test that checked for that file and also for a non-existent file test2.pdf

    it('tests the poll task', () => {

  // The file test1.pdf exists in the downloads folder
  // but file test2.pdf does not
  
  cy.task('poll', {filename: 'test1.pdf'})            // returns immediately
    .should('eq', true)
  
  cy.task('poll', {filename: 'test2.pdf', timeout: 5000})   // after 5s
    .should('eq', false)
})

    Equivalent plain-javascript task

    This is the same task but using plain javascript

    const fs = require('fs')

module.exports = defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', {

        waitForDownload: ({filename, timeout= 30_000}) => {
          const filepath = path.resolve(config.downloadsFolder, filename)
          return new Promise(resolve => {
            let stopPolling = false
            setTimeout(() => stopPolling = true, timeout)

            function check() {
              if (fs.existsSync(filepath)) {
                resolve(true)
              } else {
                if (stopPolling) {
                  resolve(false)
                } else {
                  setTimeout(() => check(), 100)  // check again after 100ms
                }
              }
            }
            check()
          })
        }
      });
    },
  },
})
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  2. 0

    You can avoid using 3-rd party libs by creating a function like this and invoking it at the start of your tasks:

    const fs = require('fs');

const sleep = time => new Promise(res => {
    setTimeout(res, time);
});

const verifyFileDownloaded = async filePath => {
    const MAX_POLLS = 10;
    const POLL_INTERVAL = 1000;
    
    for (let i = 0; i < MAX_POLLS; i++) {
        if (fs.existsSync(filePath)) {
            return;
        }

        await sleep(POLL_INTERVAL);
    }

    throw new Error(`Failed to detect the file at the path "${filePath}" within the timeout of ${POLL_INTERVAL / 1000 * MAX_POLLS} seconds`);
}
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