Gleb Bahmutov, PhD

VP of Engineering, Cypress.io

Cypress: testing without Selenium

Part 2

C / C++ / C# / Java / CoffeeScript / JavaScript / Node / Angular / Vue / Cycle.js / functional / testing

Contents: Part 2

  • Cypress architecture

  • Declarative test syntax

  • Code coverage updates

  • CircleCI Orbs

  • Component and API testing

When should I write an end-to-end test?

planning

coding

deploying

staging / QA

production

E2E

E2E

Users

planning

coding

deploying

staging / QA

production

πŸ’΅

E2E

E2E

Users

πŸ’΅

🐞$0

πŸ’΅

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πŸ’°

πŸ’°

πŸ’΅

πŸ’΅

planning

coding

deploying

staging / QA

production

πŸ’΅

E2E

E2E

Users

πŸ’΅

🐞$0

πŸ’΅

πŸ’°

πŸ’°

πŸ’°

πŸ’°

πŸ’°

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Answer: E2E

πŸ’΅

πŸ’΅

πŸ’΅

Cypress Architecture:

Optimized for Developers to do End-to-end testing

Cypress Architecture

There are two iframes: one for the app, one for the specs

specs

app

Cypress

App

Browser

launch browser

PROXY="Cypress App"

Cypress

App

Browser

launch browser

PROXY="Cypress App"

GET domain.com

Cypress

App

Browser

launch browser

PROXY="Cypress App"

GET domain.com

GET domain.com

Cypress

App

Browser

launch browser

PROXY="Cypress App"

GET domain.com

GET domain.com

Self-signed

Certificate for

domain.com

(problems with corporate proxies

see GH issues at cypress-io/cypress)Β 

Cypress

App

Browser

launch browser

PROXY="Cypress App"

GET domain.com

Self-signed

Certificate for

domain.com

inject <script>document.domain = ...

DOM

storage

location

cookies

Cypress tests run in the same browser

specs

app

DOM

storage

location

cookies

Cypress acts as a proxy for your app

specs

app

iframes

logins

specs

app

But how is this different from tool X running outside the browser?

Hint: browsers are complicated

Node to Browser actions are hard

Node

Browser

Command visibility and actionability checks for

cy.click()

Visibility checks for

cy.click()

Node

Cy backend

cy.task(name, ...args)
on('task', {
Β  name: (...args) => ...
})

Browser to Node is easy

cy.task
cy.exec
cy.request

(and you only send data, not code)

Browser to Node is easy

cy.task

Browser to Node is easy

Run any Node code from your test

it('finds record in the database', () => {
  // random text to avoid confusion
  const id = Cypress._.random(1, 1e6)
  const title = `todo ${id}`
  cy.get('.new-todo').type(`${title}{enter}`)
  cy.task('hasSavedRecord', title).should('equal', true)
})

Observe Database Effect

runs in the browser

const hasRecordAsync = (title, ms) => {
  // use promise-retry or convergence
  ...
}

module.exports = (on, config) => {
  on('task', {
    hasSavedRecord (title, ms = 3000) {
      return hasRecordAsync(title, ms)
    }
  })
}

runs in Node in cypress/plugins/index.js

Observe Database Effect

task completes as soon as the server gets POST from the app and saves record to DB

task checks for wrong title and eventually times out

it('changes the URL when "awesome" is clicked', () => {
  cy.visit('/my/resource/path')

  cy.get('.awesome-selector')
    .click()

  cy.url()
    .should('include', 
            '/my/resource/path#awesomeness')
})

Declarative Syntax

there are no async / awaits or promise chains

Tests should read naturally

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('https://example.com');
  await page.screenshot({path: 'example.png'});

  await browser.close();
})();

Puppeteer

test('My Test', async t => {
    await t
        .setNativeDialogHandler(() => true)
        .click('#populate')
        .click('#submit-button');

    const location = await t.eval(() => window.location);

    await t.expect(location.pathname)
        .eql('/testcafe/example/thank-you.html');
});

TestCafe

it('changes the URL when "awesome" is clicked', () => {
  const user = cy

  user.visit('/my/resource/path')

  user.get('.awesome-selector')
    .click()

  user.url()
    .should('include', 
            '/my/resource/path#awesomeness')
})

Cypress is like a real user

Dear user,Β 

  1. open url localhost:3000/my/resource/path
  2. click on button "foo"
  3. check if url includes /my/resource/path#awesomenessΒ 

more details: "End-to-end Testing Is Hard - But It Doesn't Have to Be​" ReactiveConf 2018 https://www.youtube.com/watch?v=swpz0H0u13k

But how does it FEEL?

When I test with Cypress

DOM

Network

storage

DOM only βœ…

End-to-end tests

Network stubs βœ…

Application code stubs βœ…

End-to-end tests

Local TDD : stub first

Mature app : remove stubs

Tests against production: stub or non-destructive tests only

Keep your test balance

unit / E2E tests for happy path

error handling

tests based on crashes

50%

20%

30%

Writing tests

Where should I put my end-to-end tests?

Start

  • Cypress tests in a separate repo

Evaluate Cypress and write first end-to-end tests in minutes

Mature

  • Cypress tests in same repo as the web application

  • Write tests sooner
  • Run tests on each commit
  • Share code between app and tests

Organization

  • Use folder structure

  • Run some specs

$ npx cypress run --spec 'cypress/integration/feature-a/*'

If you can write E2E tests in a framework-agnostic way

You can replace framework X with Y

(without breaking things)

Code Coverage

  • Instrument the code

  • Run the tests

  • See if we reached every line of code

Coverage is hard

Code coverage

is tricky

const isEmail = (s) =>
  /^\w+@\w+\.\w{3,4}$/.test(s)

// 1 test = 100% code coverage
​(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

Code coverage

vs

Data coverage

mocha -r data-cover spec.js

I don't think code coverage is useful for end-to-end tests

You cannot test every part of your car by driving around

user interface

application code

vendor code

polyfills

there is probably a lot of app code unreachable through the UI alone

beforeEach(() => {
  cy.visit('/')
})
it('works', function () {
  cy.get('.new-todo').type('first todo{enter}')
  cy.get('.new-todo').type('second todo{enter}')
  cy.get('.todo-list li').should('have.length', 2)
})

What does this test cover?

Cypress.Commands.overwrite('type', 
  (type, $el, text, options) => {

  rememberSelector($el)

  return type($el, text, options)
})

Track "cy.type" elements

Highlight tested element

Elements NOT covered by the test

beforeEach(() => {
  cy.visit('/')
})
it('works', function () {
  cy.get('.new-todo').type('first todo{enter}')
  cy.get('.new-todo').type('second todo{enter}')
  cy.get('.todo-list li').should('have.length', 2)
    .first().find(':checkbox').check()

  cy.contains('.filters a', 'Active').click()
  cy.url().should('include', 'active')

  cy.contains('.filters a', 'Completed').click()
  cy.url().should('include', 'completed')

  cy.contains('.filters a', 'All').click()
  cy.url().should('include', '#/')
})

Extend test to cover more elements

The test did not cover "Clear completed" button

Problem: only "check" this box,

but not "uncheck"

Paid Features πŸ’΅

Paid Features πŸ’΅: artifacts

test output, video, screenshots

Cypress on CI

(continuous integration server like Jenkins)

  • "cypress open" - GUI interactive mode

  • "cypress run" - headless mode

Cypress CLI has 2 main commands

full video of the run, screenshots of everyΒ  failure

  • Every CI should be good

  • Or use a Docker image we provide

Running E2E on CI

Making it easy for users is not easy

version: 2
jobs:
  test:
    docker:
      - image: cypress/base:10
    steps:
      - checkout
      # restore folders with npm dependencies and Cypress binary
      - restore_cache:
          keys:
            - cache-{{ checksum "package.json" }}
      # install npm dependencies and Cypress binary
      # if they were cached, this step is super quick
      - run:
          name: Install dependencies
          command: npm ci
      - run: npm run cy:verify
      # save npm dependencies and Cypress binary for future runs
      - save_cache:
          key: cache-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      # start server before starting tests
      - run:
          command: npm start
          background: true
      - run: npm run e2e:record

workflows:
  version: 2
  build:
    jobs:
      - test

Docker image

typical CI config file

version: 2
jobs:
  test:
    docker:
      - image: cypress/base:10
    steps:
      - checkout
      # restore folders with npm dependencies and Cypress binary
      - restore_cache:
          keys:
            - cache-{{ checksum "package.json" }}
      # install npm dependencies and Cypress binary
      # if they were cached, this step is super quick
      - run:
          name: Install dependencies
          command: npm ci
      - run: npm run cy:verify
      # save npm dependencies and Cypress binary for future runs
      - save_cache:
          key: cache-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      # start server before starting tests
      - run:
          command: npm start
          background: true
      - run: npm run e2e:record

workflows:
  version: 2
  build:
    jobs:
      - test

Docker image

Caching

Caching

typical CI config file

version: 2
jobs:
  test:
    docker:
      - image: cypress/base:10
    steps:
      - checkout
      # restore folders with npm dependencies and Cypress binary
      - restore_cache:
          keys:
            - cache-{{ checksum "package.json" }}
      # install npm dependencies and Cypress binary
      # if they were cached, this step is super quick
      - run:
          name: Install dependencies
          command: npm ci
      - run: npm run cy:verify
      # save npm dependencies and Cypress binary for future runs
      - save_cache:
          key: cache-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      # start server before starting tests
      - run:
          command: npm start
          background: true
      - run: npm run e2e:record

workflows:
  version: 2
  build:
    jobs:
      - test

Docker image

Caching

Caching

Install

typical CI config file

version: 2
jobs:
  test:
    docker:
      - image: cypress/base:10
    steps:
      - checkout
      # restore folders with npm dependencies and Cypress binary
      - restore_cache:
          keys:
            - cache-{{ checksum "package.json" }}
      # install npm dependencies and Cypress binary
      # if they were cached, this step is super quick
      - run:
          name: Install dependencies
          command: npm ci
      - run: npm run cy:verify
      # save npm dependencies and Cypress binary for future runs
      - save_cache:
          key: cache-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      # start server before starting tests
      - run:
          command: npm start
          background: true
      - run: npm run e2e:record

workflows:
  version: 2
  build:
    jobs:
      - test

Docker image

Caching

Caching

maybe start app

typical CI config file

Install

version: 2
jobs:
  test:
    docker:
      - image: cypress/base:10
    steps:
      - checkout
      # restore folders with npm dependencies and Cypress binary
      - restore_cache:
          keys:
            - cache-{{ checksum "package.json" }}
      # install npm dependencies and Cypress binary
      # if they were cached, this step is super quick
      - run:
          name: Install dependencies
          command: npm ci
      - run: npm run cy:verify
      # save npm dependencies and Cypress binary for future runs
      - save_cache:
          key: cache-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      # start server before starting tests
      - run:
          command: npm start
          background: true
      - run: npm run e2e:record

workflows:
  version: 2
  build:
    jobs:
      - test

Docker image

Caching

Caching

typical CI config file

Install

run tests

maybe start app

Copy / paste / tweak until CI passes πŸ™

I have 100s of tests ...

$ npx cypress run --record --parallel

Cypress v3.1.0

Spin N CI machines and

defaults: &defaults
  working_directory: ~/app
  docker:
    - image: cypress/browsers:chrome67

version: 2
jobs:
  build:
    <<: *defaults
    steps:
      - checkout
      # find compatible cache from previous build,
      # it should have same dependencies installed from package.json checksum
      - restore_cache:
          keys:
            - cache-{{ .Branch }}-{{ checksum "package.json" }}
      - run:
          name: Install Dependencies
          command: npm ci
      # run verify and then save cache.
      # this ensures that the Cypress verified status is cached too
      - run: npm run cy:verify
      # save new cache folder if needed
      - save_cache:
          key: cache-{{ .Branch }}-{{ checksum "package.json" }}
          paths:
            - ~/.npm
            - ~/.cache
      - run: npm run types
      - run: npm run stop-only
      # all other test jobs will run AFTER this build job finishes
      # to avoid reinstalling dependencies, we persist the source folder "app"
      # and the Cypress binary to workspace, which is the fastest way
      # for Circle jobs to pass files
      - persist_to_workspace:
          root: ~/
          paths:
            - app
            - .cache/Cypress

  4x-electron:
    <<: *defaults
    # tell CircleCI to execute this job on 4 machines simultaneously
    parallelism: 4
    steps:
      - attach_workspace:
          at: ~/
      - run:
          command: npm start
          background: true
      # runs Cypress test in load balancing (parallel) mode
      # and groups them in Cypress Dashboard under name "4x-electron"
      - run: npm run e2e:record -- --parallel --group $CIRCLE_JOB

workflows:
  version: 2
  # this workflow has 4 jobs to show case Cypress --parallel and --group flags
  # "build" installs NPM dependencies so other jobs don't have to
  #   β”” "1x-electron" runs all specs just like Cypress pre-3.1.0 runs them
  #   β”” "4x-electron" job load balances all specs across 4 CI machines
  #   β”” "2x-chrome" load balances all specs across 2 CI machines and uses Chrome browser
  build_and_test:
    jobs:
      - build
      # this group "4x-electron" will load balance all specs
      # across 4 CI machines
      - 4x-electron:
          requires:
            - build

Parallel config is ... more complicated

typical CI config file

- install + run jobs

- workspace

- parallel flags

# first, install Cypress, then run all tests (in parallel)
stages:
  - build
  - test

# to cache both npm modules and Cypress binary we use environment variables
# to point at the folders we can list as paths in "cache" job settings
variables:
  npm_config_cache: "$CI_PROJECT_DIR/.npm"
  CYPRESS_CACHE_FOLDER: "$CI_PROJECT_DIR/cache/Cypress"

# cache using branch name
# https://gitlab.com/help/ci/caching/index.md
cache:
  key: ${CI_COMMIT_REF_SLUG}
  paths:
    - .npm
    - cache/Cypress
    - node_modules

# this job installs NPM dependencies and Cypress
install:
  image: cypress/base:10
  stage: build

  script:
    - npm ci
    - $(npm bin)/print-env CI
    - npm run cy:verify

# all jobs that actually run tests can use the same definition
.job_template: &job
  image: cypress/base:10
  stage: test
  script:
    # print CI environment variables for reference
    - $(npm bin)/print-env CI
    # start the server in the background
    - npm run start:ci &
    # run Cypress test in load balancing mode, pass id to tie jobs together
    - npm run e2e:record -- --parallel --ci-build-id $CI_PIPELINE_ID --group electrons

# actual job definitions
# all steps are the same, they come from the template above
electrons-1:
  <<: *job
electrons-2:
  <<: *job
electrons-3:
  <<: *job
electrons-4:
  <<: *job
electrons-5:
  <<: *job
pipeline {
  agent {
    // this image provides everything needed to run Cypress
    docker {
      image 'cypress/base:10'
    }
  }

  stages {
    // first stage installs node dependencies and Cypress binary
    stage('build') {
      steps {
        // there a few default environment variables on Jenkins
        // on local Jenkins machine (assuming port 8080) see
        // http://localhost:8080/pipeline-syntax/globals#env
        echo "Running build ${env.BUILD_ID} on ${env.JENKINS_URL}"
        sh 'npm ci'
        sh 'npm run cy:verify'
      }
    }

    stage('start local server') {
      steps {
        // start local server in the background
        // we will shut it down in "post" command block
        sh 'nohup npm start &'
      }
    }

    // this tage runs end-to-end tests, and each agent uses the workspace
    // from the previous stage
    stage('cypress parallel tests') {
      environment {
        // we will be recordint test results and video on Cypress dashboard
        // to record we need to set an environment variable
        // we can load the record key variable from credentials store
        // see https://jenkins.io/doc/book/using/using-credentials/
        CYPRESS_RECORD_KEY = credentials('cypress-example-kitchensink-record-key')
        // because parallel steps share the workspace they might race to delete
        // screenshots and videos folders. Tell Cypress not to delete these folders
        CYPRESS_trashAssetsBeforeRuns = 'false'
      }

      // https://jenkins.io/doc/book/pipeline/syntax/#parallel
      parallel {
        // start several test jobs in parallel, and they all
        // will use Cypress Dashboard to load balance any found spec files
        stage('tester A') {
          steps {
            echo "Running build ${env.BUILD_ID}"
            sh "npm run e2e:record:parallel"
          }
        }

        // second tester runs the same command
        stage('tester B') {
          steps {
            echo "Running build ${env.BUILD_ID}"
            sh "npm run e2e:record:parallel"
          }
        }
      }

    }
  }

  post {
    // shutdown the server running in the background
    always {
      echo 'Stopping local server'
      sh 'pkill -f http-server'
    }
  }
}
language: node_js

node_js:
  # Node 10.3+ includes npm@6 which has good "npm ci" command
  - 10.8

cache:
  # cache both npm modules and Cypress binary
  directories:
    - ~/.npm
    - ~/.cache
  override:
    - npm ci
    - npm run cy:verify

defaults: &defaults
  script:
    #   ## print all Travis environment variables for debugging
    - $(npm bin)/print-env TRAVIS
    - npm start -- --silent &
    - npm run cy:run -- --record --parallel --group $STAGE_NAME
    # after all tests finish running we need
    # to kill all background jobs (like "npm start &")
    - kill $(jobs -p) || true

jobs:
  include:
    # we have multiple jobs to execute using just a single stage
    # but we can pass group name via environment variable to Cypress test runner
    - stage: test
      env:
        - STAGE_NAME=1x-electron
      <<: *defaults
    # run tests in parallel by including several test jobs with same name variable
    - stage: test
      env:
        - STAGE_NAME=4x-electron
      <<: *defaults
    - stage: test
      env:
        - STAGE_NAME=4x-electron
      <<: *defaults
    - stage: test
      env:
        - STAGE_NAME=4x-electron
      <<: *defaults
    - stage: test
      env:
        - STAGE_NAME=4x-electron
      <<: *defaults

Different CIs

Copy / paste / tweak until CI passes 😑

Good news about Continuous Integration: Orbs

CircleCI Orbs

Reusable CI configuration code

version: 2.1
orbs:
  cypress: cypress-io/cypress@1
workflows:
  build:
    jobs:
      - cypress/run

CircleCI Orbs

circle.yml

version: 2.1
orbs:
  cypress: cypress-io/cypress@1
workflows:
  build:
    jobs:
      - cypress/run:
          record: true

record tests on Cypress Dashboard

circle.yml

version: 2.1
orbs:
  cypress: cypress-io/cypress@1
workflows:
  build:
    jobs:
      - cypress/install
      - cypress/run:
          requires:
            - cypress/install
          record: true
          parallel: true
          parallelism: 10

Parallel run scenario

CircleCI Orbs

circle.yml

Orbs: best thing in CI since Docker

Orbs: Cypress team can help you run our tool on CircleCI

Cypress Orb Source

Cool Things You Can do With Cypress

HTTP API testing

Test components from frameworks

E2E

integration

unit

Cypress

$ npm install -D cypress cypress-vue-unit-test
const mountVue = require('cypress-vue-unit-test')
describe('My Vue', () => {
  beforeEach(mountVue(/* my Vue code */, /* options */))
  it('renders', () => {
    // Any Cypress command
    // Cypress.vue is the mounted component reference
  })
})

Vue component test demo with Cypress

Interact, inspect, use

Test components from these frameworks with ease

  • network control
  • method spy / stub
  • GUI

E2E

integration

unit

Web Application

Jest

Cypress

E2E

integration

unit

Web Application

Jest

Cypress

API tests

const request = require('supertest')
const app = require(...)
request(app)
  .get('/user')
  .expect('Content-Type', /json/)
  .expect('Content-Length', '15')
  .expect(200, {
    name: 'Joe',
    age: 33
  })

Replace API tests

it('returns JSON', () => {
  cy.request('http://localhost:3000/todos')
    .its('headers')
    .its('content-type')
    .should('include', 'application/json')
})

With Cypress API tests

and gain test UI

and gain:

  • fixtures

  • stubbing

  • custom commands

  • longer tests

  • mixed UI / API tests

Coming soon

  • Retries / flake factor

  • Cross-browser

  • Full network stubbing

  • so many more ideas ...

IE11

Thank you πŸ‘

Cypress: testing without Selenium Part 2

By Gleb Bahmutov

Cypress: testing without Selenium Part 2

* Cypress architecture * Declarative test syntax * Code coverage updates * CircleCI Orbs * Component and API testing. SeleniumCamp 2019 Kyiv, Ukraine Video at https://www.youtube.com/watch?v=AYlFF_KTFl8

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