invalid-amp.php

<?php
/**
 * Plugin Name: Invalid AMP
 * Description: Intentionally outputs invalid AMP.
 */

/**
 * Outputs a disallowed <script> for post types of 'page' only.
 */
add_action( 'wp_print_footer_scripts', function() {
	if ( 'page' === get_post_type() ) :
		?>
		<script type="text/javascript">
			console.log( 'Invalid AMP' );
		</script>
		<?php
	endif;
} );

/**
 * Enqueues scripts and stylesheets to cause AMP validation errros.
 */
add_action( 'wp_enqueue_scripts', function() {
	wp_enqueue_script( 'iu-foo-a', 'http://example.com/foo-a' );
	wp_enqueue_script( 'iu-foo-b', 'http://example.com/foo-b' );

	wp_enqueue_style( 'iu-example-a', 'http://example.com/example-a' );
	wp_enqueue_style( 'iu-example-b', 'http://example.com/example-b' );
} );