readFile

Read a file and yield its contents.

Syntax

cy.readFile(filePath)
cy.readFile(filePath, encoding)
cy.readFile(filePath, options)
cy.readFile(filePath, encoding, options)

Usage

Correct Usage

cy.readFile('menu.json')

Arguments

filePath (String)

A path to a file within the project root (the directory that contains the Cypress configuration file).

encoding (String)

The encoding to be used when reading the file. The following encodings are supported:

• 'ascii'
• 'base64'
• 'binary'
• 'hex'
• 'latin1'
• 'utf8'
• 'utf-8'
• 'ucs2'
• 'ucs-2'
• 'utf16le'
• 'utf-16le'
• null

Using null explicitly will return the file as a Buffer, regardless of file extension.

options (Object)

Pass in an options object to change the default behavior of cy.readFile().

Yields

• cy.readFile() yields the contents of the file.

Examples

Text

Read a .txt file

For any file other than JSON, the contents of the file are returned.

// path/to/message.txt

Hello World

cy.readFile('path/to/message.txt').should('eq', 'Hello World') // true

JSON

For JSON, the contents yielded are parsed into JavaScript and returned.

// data.json

{
  "name": "Eliza",
  "email": "eliza@example.com"
}

cy.readFile('path/to/data.json').its('name').should('eq', 'Eliza') // true

YAML

Get translation data from a YAML file

const YAML = require('yamljs')

cy.readFile('languages/en.yml').then((str) => {
  // parse the string into object literal
  const english = YAML.parse(str)

  cy.get('#sidebar')
    .find('.sidebar-title')
    .each(($el, i) => {
      englishTitle = english.sidebar[i]

      expect($el.text()).to.eq(englishTitle)
    })
})

Encoding

Specify the encoding with the second argument

cy.readFile('path/to/logo.png', 'base64').then((logo) => {
  // logo will be encoded as base64
  // and should look something like this:
  // aIJKnwxydrB10NVWqhlmmC+ZiWs7otHotSAAAOw==...
})

Read

cy.fixture('path/to/logo.png', null).then((logo) => {
  // logo will be read as a buffer
  // and should look something like this:
  // Buffer([0, 0, ...])
})

Playing MP3 file

cy.readFile('audio/sound.mp3', 'base64').then((mp3) => {
  const uri = 'data:audio/mp3;base64,' + mp3
  const audio = new Audio(uri)

  audio.play()
})

Notes

Existence

Default file existence assertion

By default, cy.readFile() asserts that the file exists and will fail if it does not exist. It will retry reading the file if it does not initially exist until the file exists or the command times out.

// will fail after the defaultCommandTimeout is reached
cy.readFile('does-not-exist.yaml')

Asserting file non-existence

You can assert that a file does not exist like so:

// will pass if the file does not exist
cy.readFile('does-not-exist.yaml').should('not.exist')

Read a file that might not exist

See our example on using cy.task() to read a file that may not exist.

Retries

Automatic retries

cy.readFile() will continue to read the file until it passes all of its assertions.

// if this assertion fails cy.readFile will poll the file
// until it eventually passes its assertions (or times out)
cy.readFile('some/nested/path/story.txt').should('eq', 'Once upon a time...')

Rules

Requirements

• cy.readFile() requires being chained off of cy.
• cy.readFile() requires the file must exist.
• cy.readFile() requires the file be successfully read from disk.

Assertions

• cy.readFile() will automatically retry until all chained assertions have passed.

Timeouts

• cy.readFile() can time out waiting for assertions you've added to pass.
• cy.readFile() can time out when the content being read takes a significant amount of time to encode.

Command Log

List the contents of your package.json file

cy.readFile('package.json')

The command above will display in the Command Log as:

When clicking on the readFile command within the command log, the console outputs the following:

History

See also

• cy.exec()
• cy.fixture() for a similar command with caching
• cy.task()
• cy.writeFile()