A plugin to show that an admin user really can do anything.

admin-user-can.php

<?php
/*
Plugin Name: Admin User Can
Plugin URI:  https://gist.github.com/afragen/97ac1e349316f51fd40c
Author:      Andy Fragen
Author URI:  http://thefragens.com/
Description: A plugin to show that an admin user really can do anything.
Version:     0.0.1
License:     GNU General Public License v2
License URI: http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
*/

add_action( 'admin_notices', 'fragen_auc_msg' );
function fragen_auc_msg() {
	$cap               = 'fladort';
	$current_user      = wp_get_current_user();
	$current_user_caps = $current_user->allcaps;
	$if_strpos         = false;

	if ( array_key_exists( $cap, $current_user_caps ) ) {
		$msg_arraykey = '`array_key_exists` says you have the capability "' . $cap . '"<br />';
	} else {
		$msg_arraykey = '`array_key_exists` says you don\'t have the capability "' . $cap . '".<br />';
	}

	foreach ( $current_user_caps as $key => $value ) {
		if ( ! $if_strpos ) {
			if ( strpos( $key, $cap ) ) {
				$msg_strpos = '`strpos` says you have the capability "' . $cap . '".<br />';
				$if_strpos  = true;
			} else {
				$msg_strpos = '`strpos` says you don\'t have the capability "' . $cap . '".<br />';
			}
		}
	}

	if ( is_admin() ) {
		if ( current_user_can( $cap ) ) {
			$msg = 'The current user is ' . key( $current_user->caps ) . ' and can "' . $cap . '"<br />';

		} else {
			$msg = 'The current user is ' . key( $current_user->caps ) . ' and cannot "' . $cap . '"<br />';
		}
		$user_switch = '<p>You need to use <a href="http://wordpress.org/plugins/user-switching/">User Switching plugin</a> to test completely.</p>';
		echo '<div class="error"><p>' . $user_switch . $msg . $msg_arraykey . $msg_strpos . '</p></div>';
	}
}