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☀️ Part 14: Fixtures

📚 You will learn

  • how to load and use data fixtures

+++

  • start TodoMVC application using npm start
  • open cypress/integration/14-fixtures/spec.js

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Todo: reset server using a fixture

⌨️ test "sets list of todos on the server"

  • load fixture file "cypress/integration/two-items.json"
  • post the list to "/reset" as { todos: list }

Tip: we are going to need cy.fixture

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Load fixture before each test

⌨️ test "closure variable"

let list
beforeEach(() => {
  cy.fixture('two-items')
  // then store the loaded items in variable "list"
})
it('sets list from context', () => {
  // post items to the server
})

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Store data in test context

In Mocha, hooks like before, beforeEach, it can store data in "this" object, if the callbacks use "function () { ... }" form.

beforeEach(function () {
  this.foo = 'bar'
})
it('has foo', function () {
  expect(this.foo).to.equal('bar')
})

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Load fixture before each test

⌨️ test context "this.list"

context('this.list', () => {
  beforeEach(function () {
    cy.fixture('two-items')
    // then assign value to "this.list"
  })
  it('sets list from context', function () {
    // POST "this.list" to the server using "/reset"
  })
  it('has valid list with 2 items', function () {
    // check that "this.list" has 2 items
  })
})

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⚠️ Be careful trying to replace beforeEach with before

⌨️ test context "this.list"

Try saving time by replacing beforeEach with before.

What happens? How do you solve this?

Note: Each test wipes away the previous context object. Thus "this.list" becomes undefined when the second test runs. You can use closure variable instead of "this" to get around this. This is a common problem when trying to save time on login.

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Fixtures recipe

Check out the "Fixtures" recipe in github.com/cypress-io/cypress-example-recipes repository.

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Log in once

let token
before(() => {
  cy.request(...)
    .its('response.body.token')
    .then(t => {
      // save token in closure variable
      token = t
    })
})
beforeEach(() => {
  localStorage.setItem('login-token', token)
})
// each test is logged in

Note: This is common solution to speeding up slow login - log in once, then store cookies and tokens and set them before each test.

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@ = this shortcut

⌨️ test context "@list"

beforeEach(function () {
  // cy.fixture(<filename>).as(<alias name>)
  cy.fixture('two-items').as('list')
})
it('works', function () {
  // inside test use "this.list
})

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Remember the queue of commands

it('does not work', function () {
  cy.fixture('two-items').as('list')
  // we are using "this.list" BEFORE it was set in
  // the above asynchronous call
  expect(this.list).to.have.length(2)
  cy.request('POST', '/reset', { todos: this.list })
})

Note: Walk through each line to number the order in which commands are executed

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Add command to the queue

it('works if we change the order', function () {
  cy.fixture('two-items')
    .as('list')
    .then(() => {
      // by now the fixture has been saved into "this.list"
      // check that "this.list" has 2 items
      // use it to post to the server
    })
})

Note: Using cy.then to schedule another callback will solve the problem.

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Fixtures in different encoding

Todo: in file cypress/support/index.js uncomment

require('cypress-dark/src/halloween')

Run at least one failing test

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Halloween theme

How did the test load and play MP3?

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In node_modules/cypress-dark/halloween.js

const witchLaughs = () => {
  const filename = join(getSourceFolder(), 'halloween-laugh.mp3')
  cy.readFile(filename, 'base64', { log: false }).then(mp3 => {
    const uri = 'data:audio/mp3;base64,' + mp3
    const audio = new Audio(uri)
    audio.play()
  })
}

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You can do the same with MP3 files in your fixtures folder

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

  audio.play()
})

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Other formats

cy.fixture('images/logo.png').then((logo) => {
  // logo will be encoded as base64
  // and should look something like this:
  // aIJKnwxydrB10NVWqhlmmC+ZiWs7otHotSAAAOw==...
})
cy.fixture('images/logo.png', 'binary').then((logo) => {
  // logo will be encoded as binary
  // and should look something like this:
  // 000000000000000000000000000000000000000000...
})

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readFile and writeFile

cy.readFile will retry until file exists and assertions that follow it pass

// note: path is relative to the project's root
cy.readFile('some/nested/path/story.txt')
  .should('eq', 'Once upon a time...')

on/readfile and on/writefile

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Todo readFile after POST

it('reads items loaded from fixture', () => {
  cy.fixture('two-items').then(todos => {
    // post items
    // read file 'todomvc/data.json',
    // should be equal to the loaded fixture
    // note: JSON is parsed automatically!
  })
})

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Todo readFile entered through UI

it('saves todo', () => {
  // reset data on the server
  // visit the page
  // type new todo via GUI
  // read file - it should have the item you have entered
})

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🏁 Fixtures

Fixtures are data object for testing and network stubs

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🏁 Fixtures

When loading fixtures remember JavaScript + Mocha lifecycle and this context

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🏁 Fixtures