$ npm install -D cypress

// ui-spec.js
it('loads the app', () => {
  cy.visit('http://localhost:3000')
  cy.get('.todoapp').should('be.visible')
})

cy.get('.todo-list li')     // command
  .should('have.length', 2) // assertion

{
  "retries": {
    // Configure retry attempts for `cypress run`
    // Default is 0
    "runMode": 2,
    // Configure retry attempts for `cypress open`
    // Default is 0
    "openMode": 0
  }
}

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

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
  #   └ "1x-electron" runs all specs just like Cypress pre-3.1.0 runs them
  #   └ "4x-electron" job load balances all specs across 4 CI machines
  #   └ "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

# all jobs that actually run tests can use the same definition
job_template: &job_template
  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
    - npm run e2e:record -- --parallel --group "electrons on GitLab CI"
  artifacts:
    when: always
    paths:
      - cypress/videos/**/*.mp4
      - cypress/screenshots/**/*.png
    expire_in: 1 day

# actual job definitions
# all steps are the same, they come from the template above
electrons-1:
  <<: *job_template
electrons-2:
  <<: *job_template
electrons-3:
  <<: *job_template
electrons-4:
  <<: *job_template
electrons-5:
  <<: *job_template

# 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

name: ci
on: [push, pull_request]
jobs:
  cypress-run:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout 🛎
        uses: actions/checkout@v1

      # Install NPM dependencies, 
      # cache them correctly,
      # and run all Cypress tests
      - name: Cypress run 🧪
        uses: cypress-io/github-action@v2
        with:
          start: npm start