Task command for Node operations in Cypress - Build an Automation Script

Verify reading a file content using Cypress task command

Preconditions (1)

Step 1: Open the Cypress test runner

Step 2: Run the test that calls a Cypress task to read 'sample.txt' content from Node

Step 3: Verify the content returned by the task matches 'Hello Cypress!'

✅ Expected Result: The test passes confirming the file content read via Node task matches the expected string

Automation Requirements - Cypress

Assertions Needed:

Assert the content returned from the task equals 'Hello Cypress!'

Best Practices:

Use Cypress task command to perform Node file system operations

Keep Node code in plugins or support file

Use explicit assertion with .should or expect

Avoid direct file system calls in test code

Automated Solution

Cypress

/// <reference types="cypress" />

// cypress/plugins/index.js
const fs = require('fs');

module.exports = (on, config) => {
  on('task', {
    readFileContent(filename) {
      return new Promise((resolve, reject) => {
        fs.readFile(`cypress/fixtures/${filename}`, 'utf8', (err, data) => {
          if (err) {
            return reject(err);
          }
          resolve(data);
        });
      });
    }
  });
};

// cypress/e2e/readFileTask.cy.js

describe('Read file content using Cypress task', () => {
  it('should read sample.txt content via task', () => {
    cy.task('readFileContent', 'sample.txt').then((content) => {
      expect(content).to.equal('Hello Cypress!');
    });
  });
});

The plugins/index.js file defines a Cypress task named readFileContent that uses Node's fs.readFile to read a file asynchronously from the cypress/fixtures folder. It returns a promise that resolves with the file content.

The test file readFileTask.cy.js calls this task with cy.task('readFileContent', 'sample.txt'). The returned content is then asserted to equal the expected string 'Hello Cypress!' using expect.

This approach keeps Node operations separate from browser test code and uses Cypress best practices for asynchronous tasks and assertions.

Common Mistakes - 3 Pitfalls

Calling Node fs.readFile directly inside the test without using cy.task

Not returning a promise or value from the task function

{'mistake': 'Hardcoding file paths outside the Cypress folder structure', 'why_bad': 'This reduces test portability and can cause path resolution issues on different machines.', 'correct_approach': "Use relative paths inside the Cypress project folders like 'cypress/fixtures' for test files."}

Bonus Challenge

Now add data-driven testing to read three different files ('sample1.txt', 'sample2.txt', 'sample3.txt') and verify their contents using the same task command.

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