Either the config, or the path to the module to fork. The input to the test from the mask's result. It will be converted into an array of strings to become arguments to pass to the fork. The properties to pass to the `getArgs` and `getOptions` as their this context. These properties will be got from the mask's result. The contexts for the test to be passed to `getArgs` and `getOptions`. The output from the `stdout` stream, possibly with answers fed to `stdin`. The output from the `stderr` stream, possibly with answers fed to `stdin`. The code with which the process exited.