angular-cli/packages/angular/cli/commands/e2e-long.md

The command takes an optional project name, as specified in the projects section of the angular.json workspace configuration file. When a project name is not supplied, executes the e2e builder for the default project.

To use the ng e2e command, use ng add to add a package that implements end-to-end testing capabilities. Adding the package automatically updates your workspace configuration, adding an e2e CLI builder.