Activate plugins as if `is_admin()`

[JDGrimes]

I've just run across a plugin that will only be activated properly if the activation hook is called when is_admin() is true. The underlying code is actually risky and ill-conceived. However, that aside, it brought to my attention the fact that WordPress core always activates plugins when is_admin() is true. The question is, should we simulate that in our plugin activation code? After all, the plugin related functions are all currently stored in wp-admin/includes. However, I think it is good not to rely entirely on being in the admin either. It is probably better for the activation routine not to make those kinds of assumptions. But maybe it would be best for us to allow either way to be tested, as in admin and not as in admin.

[JDGrimes]

Note that I was able to achieve this for my current situation without modifying WPPPB itself. Just add this to tests/phpunit/includes/functions.php:

$loader = WordPoints_PHPUnit_Bootstrap_Loader::instance();
$loader->add_php_file( dirname( __FILE__ ) . '/simulate-admin.php', 'before' );

And then in the simulate-admin.php file:

global $current_screen;

/**
 * The WP_Screen class.
 *
 * @since 1.0.0
 */
require_once ABSPATH . '/wp-admin/includes/class-wp-screen.php';

$current_screen = WP_Screen::get( 'test' );