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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 Cypress.Buffer instance, regardless of file extension.

options (Object)

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

OptionDefaultDescription
logtrueDisplays the command in the Command log
timeoutdefaultCommandTimeoutTime to wait for cy.readFile() to resolve before timing out

Yields ​

  • cy.readFile() yields the contents of the file.
  • The file will be read from disk again if any upcoming command (such as an assertion) in the chain fails.

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": "[email protected]"
}
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...')

Starting in Cypress v13, cy.readFile() is a query, and will continue to read the file until all chained commands of any type pass, not just assertions.

// will retry until the json file has a `users[123].name` field, and
// the assertion passes
cy.readFile('users.json').its('users.123.name').should('eq', 'John Doe')

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:

Command Log readFile

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

Console Log readFile

History​

VersionChanges
13.0.0cy.readFile() became a query
9.0.0Changed null encoding to read as Buffer
0.17.2Improved error messaging
0.17.1cy.readFile() command added

See also​

Contents