You can download it at WordPress.org if you’d like to install it on your site.

Another option is the SimpleTest for WordPress plugin, which uses SimpleTest instead of PHPUnit, doesn’t require installing a PEAR package, and lets you run both unit and  integration tests.

Either way, you can use PHP’s ReflectionClass to test private and protected methods, although purists will tell you that’s not proper.

The first method sets a flag inside the shortcode handler when the shortcode is called, and then checks the flag in a wp_footer() callback. If the flag is true,  wp_print_scripts() is used output the JavaScript. The problem with this approach is that it doesn’t work for CSS, because CSS should be declared inside the head tag.

The second method ‘peeks ahead’ by checking to see if the shortcode exists inside the current post’s content before wp_head() is called. This is much better because it works for CSS and allows you to use wp_enqueue_script(). The one problem with it, though, is that there’s no practical way to check if someone uses do_shortcode() in a template, rather than putting the shortcode in a post.

The workaround for that is to provide a way for a theme developer to tell the plugin which pages are calling do_shortcode(), so that the plugin will know to include the files on those pages too. You can do this by checking if the scripts are loaded in your shortcode handler, and then outputing an error if they’re not. The error can contain a link to instructions for them on how to provide the list of pages to the plugin.

I’ve implemented this in version 1.1.3 of Basic Google Maps Placemarks, so you can download it or browse the source to see it working in a live environment.

Here’s a stripped-down version of what’s happening on the plugin side. loadResources() hooks in with a priority of 11 so that it loads after the theme’s code, and it calls mapShortcodeCalled() in order to check if it should load the files on the current page.

<?php

if( !class_exists('BasicGoogleMapsPlacemarks') )
{
	/**
	* A WordPress plugin that adds a custom post type for placemarks and builds a Google Map with them
	* Requires PHP5+ because of various OOP features, json_encode(), pass by reference, etc
	* Requires WordPress 3.0 because of custom post type support
	*
	* @package BasicGoogleMapsPlacemarks
	* @author Ian Dunn <redacted@iandunn.name>
	* @link http://wordpress.org/extend/plugins/basic-google-maps-placemarks/
	*/
	class BasicGoogleMapsPlacemarks
	{
		// ...

		/**
		* Constructor
		* @author Ian Dunn <redacted@iandunn.name>
		*/
		public function __construct()
		{
			// ...

			$this->mapShortcodeCalled	= false;

			// ...

			add_action( 'wp_head',								array( $this, 'outputHead' ) );
			add_action( 'wp_footer',							array( $this, 'outputFooter' ) );
			add_filter( 'the_posts', 							array( $this, 'loadResources'), 11 );
			add_shortcode( 'bgmp-map',							array( $this, 'mapShortcode') );
		}

		/**
		* Checks the current post(s) to see if they contain the map shortcode
		* @author Ian Dunn <redacted@iandunn.name>
		* @param array $posts
		* @return bool
		*/
		function mapShortcodeCalled($posts)
		{
			$this->mapShortcodeCalled = apply_filters( self::PREFIX .'mapShortcodeCalled', $this->mapShortcodeCalled );
			if( $this->mapShortcodeCalled )
				return true;

			foreach( $posts as $p )
			{
				preg_match( '/'. get_shortcode_regex() .'/s', $p->post_content, $matches );
				if( is_array($matches) &amp;amp;&amp;amp; array_key_exists(2, $matches) &amp;amp;&amp;amp; $matches[2] == 'bgmp-map' )
					return true;
			}

			return false;
		}

		/**
		* Load CSS and JavaScript files
		* @author Ian Dunn <redacted@iandunn.name>
		*/
		public function loadResources($posts)
		{
			// @todo - maybe find an action that gets run at the same time. would be better to hook there than to a filter. update faq for do_shortcode if do

			wp_register_script(
				'googleMapsAPI',
				'http'. ( is_ssl() ? 's' : '' ) .'://maps.google.com/maps/api/js?sensor=false',
				false,
				false,
				true
			);

			wp_register_script(
				'bgmp',
				plugins_url( 'functions.js', __FILE__ ),
				array( 'googleMapsAPI', 'jquery' ),
				self::BGMP_VERSION,
				true
			);

			wp_register_style(
				self::PREFIX .'style',
				plugins_url( 'style.css', __FILE__ ),
				false,
				self::BGMP_VERSION,
				false
			);

			if( $posts )
			{
				$this->mapShortcodeCalled = $this->mapShortcodeCalled( $posts );

				if( !is_admin() &amp;amp;&amp;amp; $this->mapShortcodeCalled )
				{
					wp_enqueue_script('googleMapsAPI');
					wp_enqueue_script('bgmp');
				}

				if( is_admin() || $this->mapShortcodeCalled )
					wp_enqueue_style( self::PREFIX . 'style' );
			}

			return $posts;
		}

		/**
		* Outputs elements in the <head> section of the front-end
		* @author Ian Dunn <redacted@iandunn.name>
		*/
		public function outputHead()
		{
			if( $this->mapShortcodeCalled )
			require_once( dirname(__FILE__) . '/views/front-end-head.php' );
		}

		/**
		* Outputs some initial values for the JavaScript file to use
		* @author Ian Dunn <redacted@iandunn.name>
		*/
		public function outputFooter()
		{
			if( $this->mapShortcodeCalled )
			require_once( dirname(__FILE__) . '/views/front-end-footer.php' );
		}

		/**
		* Defines the [bgmp-map] shortcode
		* @author Ian Dunn <redacted@iandunn.name>
		* @param array $attributes Array of parameters automatically passed in by WordPress
		* return string The output of the shortcode
		*/
		public function mapShortcode($attributes)
		{
			if( !wp_script_is( 'googleMapsAPI', 'queue' ) || !wp_script_is( 'bgmp', 'queue' ) || !wp_style_is( self::PREFIX .'style', 'queue' ) )
				return '<p class="error">'. BGMP_NAME .' error: JavaScript and/or CSS files aren\'t loaded. If you\'re using do_shortcode() you need to add a filter to your theme first. See <a href="http://wordpress.org/extend/plugins/basic-google-maps-placemarks/faq/">the FAQ</a> for details.</p>';

			$output = sprintf('
				<div id="%smap-canvas">
				<p>Loading map...</p>
				<p><img src="%s" alt="Loading" /></p>
				</div>',
				self::PREFIX,
				plugins_url( 'images/loading.gif', __FILE__ )
			);

			return $output;
		}

		// ...

	} // end BasicGoogleMapsPlacemarks
}

?>

The theme developer can put this code in their functions.php file to tell the plugin which pages to load the files on:

add_filter( 'the_posts', 'my_theme_name_bgmp_shortcode_check' );
function my_theme_name_bgmp_shortcode_check( $posts )
{
	$shortcodePageSlugs = array(
		'first-page-slug',
		'second-page-slug',
		'hello-world'
	);

	if( $posts )
		foreach( $posts as $p )
			if( in_array( $p->post_name, $shortcodePageSlugs ) )
				add_filter( 'bgmp_mapShortcodeCalled', 'your_theme_name_bgmp_shortcode_called' );

	return $posts;
}

function your_theme_name_bgmp_shortcode_called( $mapShortcodeCalled )
{
	return true;
}