Introduction

What you'll learn

An overview of Continuous Integration
How to run Cypress tests in Continuous Integration
How to configure Cypress in various CI Providers
How to record tests to Cypress Cloud
How to run tests in parallel on CI

What is Continuous Integration?

Setting up CI

Basics

Running Cypress in Continuous Integration is almost the same as running it locally in your terminal. You generally only need to do two things:

Install Cypress

npm install cypress --save-dev

Run Cypress

cypress run

Depending on which CI provider you use, you may need a config file. You'll want to refer to your CI provider's documentation to know where to add the commands to install and run Cypress. For more configuration examples check out our examples.

Boot your server

Challenges

Typically you will need to boot a local server prior to running Cypress. When you boot your web server, it runs as a long running process that will never exit. Because of this, you'll need it to run in the background - else your CI provider will never move onto the next command.

Backgrounding your server process means that your CI provider will continue to execute the next command after executing the signal to start your server.

Many people approach this situation by running a command like the following:

npm start & cypress run // Do not do this

The problem is - what happens if your server takes time to boot? There is no guarantee that when the next command runs (cypress run) that your web server is up and available. So your Cypress test may start and try to visit your local server before it is ready to be visited.

Solutions

Luckily, there are some solutions for this. Instead of introducing arbitrary waits (like sleep 20) you can use a better option.

wait-on module

Using the wait-on module, you can block the cypress run command from executing until your server has booted.

npm start & wait-on http://localhost:8080

cypress run

Most CI providers will automatically kill background processes so you don't have to worry about cleaning up your server process once Cypress finishes.

However, if you're running this script locally you'll have to do a bit more work to collect the backgrounded PID and then kill it after cypress run.

start-server-and-test module

If the server takes a very long time to start, we recommend trying the start-server-and-test module.

npm install --save-dev start-server-and-test

In your package.json scripts, pass the command to boot your server, the url your server is hosted on and your Cypress test command.

{
  ...
  "scripts": {
    "start": "my-server -p 3030",
    "cy:run": "cypress run",
    "test": "start-server-and-test start http://localhost:3030 cy:run"
  }
}

In the example above, the cy:run command will only be executed when the URL http://localhost:3030 responds with an HTTP status code of 200. The server will also shut down when the tests complete.

Gotchas

When working with webpack-dev-server that does not respond to HEAD requests, use an explicit GET method to ping the server like this:

{
  "scripts": {
    "test": "start-server-and-test start http-get://localhost:3030 cy:run"
  }
}

When working with local https in webpack, set an environment variable to allow local certificate:

{
  "scripts": {
    "start": "my-server -p 3030 --https",
    "cy:run": "cypress run",
    "cy:ci": "START_SERVER_AND_TEST_INSECURE=1 start-server-and-test start https-get://localhost:3030 cy:run"
  }
}

Record tests

Cypress can record your tests and make the results available in Cypress Cloud. Cloud gives you access to recorded tests - typically when running Cypress tests from your CI provider - and provides you insight into what happened when your tests ran.

Recording tests allow you to:

See the number of failed, pending and passing tests.
Get the entire stack trace of failed tests.
View screenshots taken when tests fail and when using cy.screenshot().
Watch a video of your entire test run or a clip at the point of test failure.
See which machines ran each test when parallelized.

To record tests:

Set up your project to record
Pass the --record flag to cypress run within CI.

cypress run --record --key=abc123

Read the full guide on the Cypress Cloud.

Run tests in parallel

Cypress can run tests in parallel across multiple machines.

You'll want to refer to your CI provider's documentation on how to set up multiple machines to run in your CI environment.

Once multiple machines are available within your CI environment, you can pass the --parallel flag to have your tests run in parallel.

cypress run --record --key=abc123 --parallel

Read the full guide on parallelization.

Official Cypress Docker Images

We have created an official cypress/base container with all of the required dependencies installed. You can add Cypress and go! We are also adding images with browsers pre-installed under cypress/browsers name. A typical Dockerfile would look like this:

FROM cypress/base
RUN npm install
RUN $(npm bin)/cypress run

Mounting a project directory with an existing node_modules into a cypress/base docker image will not work:

docker run -it -v /app:/app cypress/base:14.16.0 bash -c 'cypress run'
Error: the cypress binary is not installed

Instead, you should build a docker container for your project's version of cypress.

Docker images & CI examples

See our examples for additional information on our maintained images and configurations on several CI providers.

Advanced setup

Machine requirements

Hardware requirements to run Cypress depend how much memory the browser, the application under test, and the server (if running it locally) need to run the tests without crashing. Visit our System Requirements guide for minimum hardware recommendations.

Some signs that your machine may not have enough CPU or memory to run Cypress:

The recorded video artifacts have random pauses or dropped frames.
Debug logs of the CPU and memory frequently show CPU percent above 100%.
The browser crashes.

You can see the total available machine memory and the current free memory by running the cypress info command.

npx cypress info
...
Cypress Version: 6.3.0
System Platform: linux (Debian - 10.5)
System Memory: 73.8 GB free 25 GB

You can see the CPU parameters on the CI machines by executing the command below.

node -p 'os.cpus()'
[
  {
    model: 'Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz',
    speed: 3399,
    times: { user: 760580, nice: 1010, sys: 158130, idle: 1638340, irq: 0 }
  }
  ...
]

Example projects and the machine configurations used to run them on CI:

Cypress Documentation and Real World App projects run tests on the default CircleCI machine using the Docker executor on the default medium size machine with 2 vCPUs and 4GB of RAM. cypress info reports System Memory: 73.8 GB free 25 GB with CPUs reported as Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz. Note that the free memory varies on CircleCI, typically we see values anywhere from 6GB to 30GB.
Real World App also executes its tests using GitHub Actions with the default hosted runner with 2 vCPUs and 7GB of RAM. cypress info reports System Memory: 7.29 GB free 632 MB with CPUs reported as Intel(R) Xeon(R) Platinum 8171M CPU @ 2.60GHz.

Tip: if there are problems with longer specs, try splitting them into shorter ones, following this example.

Dependencies

If you are not using one of the above CI providers then make sure your system has these dependencies installed.

Linux

Ubuntu/Debian

apt-get install libgtk2.0-0 libgtk-3-0 libgbm-dev libnotify-dev libgconf-2-4 libnss3 libxss1 libasound2 libxtst6 xauth xvfb

CentOS

yum install -y xorg-x11-server-Xvfb gtk2-devel gtk3-devel libnotify-devel GConf2 nss libXScrnSaver alsa-lib

Caching

As of Cypress version 3.0, Cypress downloads its binary to the global system cache - on linux that is ~/.cache/Cypress. By ensuring this cache persists across builds you can save minutes off install time by preventing a large binary download.

Cache the ~/.cache folder after running npm install, yarn, npm ci or equivalents as demonstrated in the configs below.
Do not cache node_modules across builds. This bypasses more intelligent caching packaged with npm or yarn, and can cause issues with Cypress not downloading the Cypress binary on npm install.
If you are using npm install in your build process, consider switching to npm ci and caching the ~/.npm directory for a faster and more reliable build.
If you are using yarn, caching ~/.cache will include both the yarn and Cypress caches. Consider using yarn install --frozen-lockfile as an npm ci equivalent.
If you need to override the binary location for some reason, use CYPRESS_CACHE_FOLDER environment variable.
Make sure you are not restoring the previous cache using lax keys; then the Cypress binaries can "snowball", read Do Not Let Cypress Cache Snowball on CI.

Tip: you can find lots of CI examples with configured caching in our cypress-example-kitchensink repository.

Environment variables

You can set various environment variables to modify how Cypress runs.

Configuration Values

You can set any configuration value as an environment variable. This overrides values in the Cypress configuration.

Typical use cases would be modifying things like:

CYPRESS_BASE_URL
CYPRESS_VIDEO_COMPRESSION
CYPRESS_REPORTER
CYPRESS_INSTALL_BINARY

Refer to the Environment Variables recipe for more examples.

Record Key

If you are recording your runs on a public project, you'll want to protect your Record Key. Learn why.

Instead of hard coding it into your run command like this:

cypress run --record --key abc-key-123

You can set the record key as the environment variable, CYPRESS_RECORD_KEY, and we'll automatically use that value. You can now omit the --key flag when recording.

cypress run --record

Typically you'd set this inside of your CI provider.

CircleCI Environment Variable

TravisCI Environment Variable

Git information

Cypress uses the @cypress/commit-info package to extract git information to associate with the run (e.g. branch, commit message, author).

It assumes there is a .git folder and uses Git commands to get each property, like git show -s --pretty=%B to get commit message, see src/git-api.js.

Under some environment setups (e.g. docker/docker-compose) if the .git directory is not available or mounted, you can pass all git related information under custom environment variables.

Branch: COMMIT_INFO_BRANCH
Message: COMMIT_INFO_MESSAGE
Author email: COMMIT_INFO_EMAIL
Author: COMMIT_INFO_AUTHOR
SHA: COMMIT_INFO_SHA
Remote: COMMIT_INFO_REMOTE

If the commit information is missing in the Cypress Cloud run then GitHub Integration or other tasks might not work correctly. To see the relevant Cypress debug logs, set the environment variable DEBUG on your CI machine and inspect the terminal output to see why the commit information is unavailable.

DEBUG=commit-info,cypress:server:record

Custom Environment Variables

You can also set custom environment variables for use in your tests. These enable your code to reference dynamic values.

export "EXTERNAL_API_SERVER=https://corp.acme.co"

And then in your tests:

cy.request({
  method: 'POST',
  url: Cypress.env('EXTERNAL_API_SERVER') + '/users/1',
  body: {
    foo: 'bar',
    baz: 'quux',
  },
})

Refer to the dedicated Environment Variables Guide for more examples.

Module API

Oftentimes it can be less complex to programmatically control and boot your servers with a Node script.

If you're using our Module API then you can write a script that boots and then shuts down the server later. As a bonus, you can work with the results and do other things.

// scripts/run-cypress-tests.js

const cypress = require('cypress')
const server = require('./lib/my-server')

// start your server
return server.start().then(() => {
  // kick off a cypress run
  return cypress.run().then((results) => {
    // stop your server when it's complete
    return server.stop()
  })
})

node scripts/run-cypress-tests.js

Common problems and solutions

Missing binary

When npm or yarn install the cypress package, a postinstall hook is executed that downloads the platform-specific Cypress binary. If the hook is skipped for any reason the Cypress binary will be missing (unless it was already cached).

To better diagnose the error, add commands to get information about the Cypress cache to your CI setup. This will print where the binary is located and what versions are already present.

npx cypress cache path
npx cypress cache list

If the required binary version is not found in the cache, you can try the following:

Clean your CI's cache using your CI's settings to force a clean npm install on the next build.
Run the binary install yourself by adding the command npx cypress install to your CI script. If there is a binary already present, it should finish quickly.

See bahmutov/yarn-cypress-cache for an example that runs the npx cypress install command to ensure the Cypress binary is always present before the tests begin.

In Docker

If you are running long runs on Docker, you need to set the ipc to host mode. This issue describes exactly what to do.

Xvfb

When running on Linux, Cypress needs an X11 server; otherwise it spawns its own X11 server during the test run. When running several Cypress instances in parallel, the spawning of multiple X11 servers at once can cause problems for some of them. In this case, you can separately start a single X11 server and pass the server's address to each Cypress instance using DISPLAY variable.

First, spawn the X11 server in the background at some port, for example :99. If you have installed xvfb on Linux or if you are using one of our Docker images from cypress-docker-images, the tools below should be available.

Xvfb :99 &

Second, set the X11 address in an environment variable

export DISPLAY=:99

Start Cypress as usual

npx cypress run

After all tests across all Cypress instances finish, kill the Xvfb background process using pkill

pkill Xvfb

In certain Linux environments, you may experience connection errors with your X11 server. In this case, you may need to start Xvfb with the following command:

Xvfb -screen 0 1024x768x24 :99 &

Cypress internally passes these Xvfb arguments, but if you are spawning your own Xvfb, you would need to pass these arguments. This is necessary to avoid using 8-bit color depth with Xvfb, which will prevent Chrome or Electron from crashing.

Running headless tests without Xvfb

Using the ELECTRON_RUN_AS_NODE=1 env var is experimental and not fully tested, so may not work in all environments.

Chromium based browsers and Firefox can spawn without Xvfb when run via the --headless flag. If you're testing against either of those browsers using the --browser flag, you can opt out of Cypress spawning an X11 server by setting the environment variable ELECTRON_RUN_AS_NODE=1.

Electron cannot be run without an X11 server. Cypress's default browser is Electron and won't be able to launch if you set this environment variable. Likewise, Cypress's interactive mode (running via cypress open) is run via Electron and cannot be opened without an X11 server.

Colors

If you want colors to be disabled, you can pass the NO_COLOR environment variable to disable colors. You may want to do this if ASCII characters or colors are not properly formatted in your CI.

NO_COLOR=1 cypress run

Workshop

Cypress team has created a full workshop showing how to run Cypress on popular CI providers. Find the workshop at github.com/cypress-io/cypress-workshop-ci.