readFile

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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 cypress.json).

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

options (Object)

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

Option Default Description
log true Displays the command in the Command log
timeout defaultCommandTimeout Time to wait for cy.readFile() to resolve before timing out

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": "[email protected]"
}
cy.readFile('path/to/data.json').its('name').should('eq', 'Eliza') // true

YAML

Get translation data from 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==...
})

Notes

Existence

Default Assertions: file existence

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')

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. Anything preventing this such as OS permission issues will cause it to fail.

Assertions

  • cy.readFile() will automatically retry itself until assertions you've chained all pass.

Timeouts

  • cy.readFile() can time out waiting for assertions you've added to pass.

Command Log

List the contents of cypress.json

cy.readFile('cypress.json')

The command above will display in the Command Log as:

Command Log

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

Console Log

See also