Form submission handler for simpletest_settings_form().
function simpletest_settings_form_submit($form, &$form_state) {
config('simpletest.settings')
->set('clear_results', $form_state['values']['simpletest_clear_results'])
->set('verbose', $form_state['values']['simpletest_verbose'])
->set('httpauth.method', $form_state['values']['simpletest_httpauth_method'])
->set('httpauth.username', $form_state['values']['simpletest_httpauth_username'])
->set('httpauth.password', $form_state['values']['simpletest_httpauth_password'])
->save();
}