cy.readFile() assertions in Cypress

Introduction

We use cy.readFile() to check the contents of a file during tests. This helps us make sure the file has the right data.

To verify a downloaded file contains expected text or data.

To check if a configuration file has correct settings after an action.

To confirm a log file includes specific messages after running a test.

To ensure a saved report file matches the expected format and content.

Syntax

Cypress

cy.readFile('path/to/file').should('include', 'expected text')

The path/to/file is relative to the project root.

You can use different assertions like include, equal, or contain to check file content.

Examples

This checks if the file sample.txt contains the text 'Hello World'.

Cypress

cy.readFile('cypress/fixtures/sample.txt').should('include', 'Hello World')

This verifies the JSON file exactly matches the given object.

Cypress

cy.readFile('data/config.json').should('deep.equal', { theme: 'dark', version: 1 })

This asserts the log file contains the word 'Error' anywhere inside.

Cypress

cy.readFile('logs/app.log').should('contain', 'Error')

Sample Program

This test reads the file greeting.txt and checks if it includes the word 'Welcome'.

Cypress

describe('File content test', () => {
  it('checks if the file contains expected text', () => {
    cy.readFile('cypress/fixtures/greeting.txt').should('include', 'Welcome')
  })
})

Important Notes

Make sure the file path is correct and the file exists before running the test.

Use should assertions to wait for the file read to complete before checking content.

You can read JSON files and assert their structure using deep.equal.

Summary

cy.readFile() helps test file contents easily.

Use assertions like include, contain, or deep.equal to check file data.

It is useful for verifying downloads, configs, logs, and reports.