bad-plugin-with-fatal-errors.php

<?php
/**
 * Plugin Name:     Bad plugin with fatal errors
 * Description:     For testing purposes only.
 * Author:          Pierre Gordon
 * Version:         0.1.0
 * License:         GPLv2 or later
 */

// All credit goes to Weston Ruter <https://github.com/westonruter>
// Code below is adapted from an example given in https://github.com/ampproject/amp-wp/issues/4580.

add_action( 'wp_footer', function() {
	for ( $i = 0; $i < 8; $i++ ) {
		if ( $i >= 4 && AMP_Validation_Manager::$is_validate_request ) {
			throw new Exception( 'FAIL' );
		}
		echo "<script>// bad: $i</script>";
	}
} );

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c.