-`command`<[string]> Shell command to start. For example `npm run start`..
-`port` ?<[int]> The port that your http server is expected to appear on. It does wait until it accepts connections. Either `port` or `url` should be specified.
-`url` ?<[string]> The url on your http server that is expected to return a 2xx, 3xx, 400, 401, 402, or 403 status code when the server is ready to accept connections. Redirects (3xx status codes) are being followed and the new location is checked. Either `port` or `url` should be specified.
-`ignoreHTTPSErrors` ?<[boolean]> Whether to ignore HTTPS errors when fetching the `url`. Defaults to `false`.
-`timeout` ?<[int]> How long to wait for the process to start up and be available in milliseconds. Defaults to 60000.
-`reuseExistingServer` ?<[boolean]> If true, it will re-use an existing server on the `port` or `url` when available. If no server is running on that `port` or `url`, it will run the command to start a new server. If `false`, it will throw if an existing process is listening on the `port` or `url`. This should be commonly set to `!process.env.CI` to allow the local dev server when running tests locally.
-`stdout` ?<["pipe"|"ignore"]> If `"pipe"`, it will pipe the stdout of the command to the process stdout. If `"ignore"`, it will ignore the stdout of the command. Default to `"ignore"`.
-`stderr` ?<["pipe"|"ignore"]> Whether to pipe the stderr of the command to the process stderr or ignore it. Defaults to `"pipe"`.
-`cwd` ?<[string]> Current working directory of the spawned process, defaults to the directory of the configuration file.
-`env` ?<[Object]<[string], [string]>> Environment variables to set for the command, `process.env` by default.