Cypress error "The automation client disconnected. Cannot continue running tests." when running in Docker

Question

I'm getting the following error when running a Cypress test suite in a Docker container:

The automation client disconnected. Cannot continue running tests.

Using this command, running in a cypress/browsers:node12.6.0-chrome75 container:

cypress run --browser=chrome

Answer 1

This seems to occur when running out of shm space.

By default, Docker creates a container with a /dev/shm shared memory space of 64MB. This is typically too small for Chrome and could cause Chrome to crash.

I have found two options to resolve this:

1. Disable usage of /dev/shm:

// cypress/plugins/index.js

module.exports = (on, config) => {
  // ref: https://docs.cypress.io/api/plugins/browser-launch-api.html#Usage
  on('before:browser:launch', (browser = {}, args) => {
    if (browser.name === 'chrome') {
      args.push('--disable-dev-shm-usage')
      return args
    }

    return args
  })
}

2. Increase the size of /dev/shm in the container:

Run the container with docker run --shm-size=1gb (or whatever size you want)