Script to test changes to themes in https://core.trac.wordpress.org/ticket/59316

benchmark-theme-web-vitals.php

<?php
/**
 * Benchmark Web Vitals for Themes with Script Loading Strategies.
 *
 * USAGE:
 * 1. Place this script is in the root of the WordPress/wordpress-develop Git repo; make sure environment is started.
 * 2. Fetch the trac-59316 branch from https://github.com/WordPress/wordpress-develop/pull/5170.
 * 3. Clone the GoogleChromeLabs/wpp-research repo, for example at ../wpp-research and run `npm install`.
 * 4. Make sure that each theme has been configured, including the Showcase page for Twenty Eleven.
 * 5. Then to invoke this script, do: WPP_RESEARCH_DIR=../wpp-research php benchmark-theme-web-vitals.php
 *
 * @package BenchmarkThemeWebVitals
 * @link https://core.trac.wordpress.org/ticket/59316
 * @author Weston Ruter
 * @copyright Google, 2023
 * @license GPL2
 */
namespace BenchmarkThemeWebVitals;
use Exception;

$themes = array(
	'twentyeleven'    => '/showcase/', // Page configured to set the showcase page template.
	'twentytwelve'    => '/sample-page/',
	'twentythirteen'  => '/sample-page/',
	'twentyfourteen'  => '/', // With featured content configured on homepage.
	'twentyfifteen'   => '/sample-page/',
	'twentysixteen'   => '/sample-page/',
	'twentyseventeen' => '/', // Because the homepage has a large header.
	'twentynineteen'  => '/sample-page/',
	'twentytwenty'    => '/sample-page/',
	'twentytwentyone' => '/sample-page/',
);

$baseline_branch = 'trunk';
$feature_branch  = 'trac-59316';
$request_number  = getenv( 'REQUEST_NUMBER' ) ? intval( getenv( 'REQUEST_NUMBER' ) ) : 20;
$home_url        = 'http://localhost:8889';

$wpp_research_dir = getenv( 'WPP_RESEARCH_DIR' );
if ( ! $wpp_research_dir || ! is_dir( $wpp_research_dir ) ) {
	fwrite( STDERR, "Missing WPP_RESEARCH_DIR environment variable.\n" );
	exit( 1 );
}

$all_results = array();

foreach ( $themes as $theme => $path ) {
	echo "# $theme\n";
	system( sprintf( 'npm run env:cli -- theme activate %s', escapeshellarg( $theme ) ) );

	$url = $home_url . $path;

	try {
		echo "Checking {$baseline_branch} branch...\n";
		system( sprintf( 'git checkout --quiet %s', escapeshellarg( $baseline_branch ) ) );
		$before_result = benchmark_web_vitals( $url, $request_number, $wpp_research_dir );

		echo "Checking {$feature_branch} branch...\n";
		system( sprintf( 'git checkout --quiet %s', escapeshellarg( $feature_branch ) ) );
		$after_result = benchmark_web_vitals( $url, $request_number, $wpp_research_dir );
	} catch ( Exception $e ) {
		fwrite( STDERR, $e->getMessage() );
		exit( 1 );
	}

	echo "$before_result => $after_result\n";
	$all_results[ $theme ] = array( $before_result, $after_result );
}

echo "\n\n";
echo "Theme, Before, After, Diff (ms), Percentage\n";
foreach ( $all_results as $theme => list( $before, $after ) ) {
	$diff = $after - $before;
	echo join(
		', ',
		array(
			$theme,
			sprintf( '%.2f', $before ),
			sprintf( '%.2f', $after ),
			( $diff > 0 ? '+' : '' ) . sprintf( '%.2f', $diff ),
			( $diff > 0 ? '+' : '-' ) . sprintf( '%.2f%%', abs( 100 - ( $after / $before ) * 100 ) ),
		)
	) . "\n";
}
function benchmark_web_vitals( string $url, int $request_number, string $wpp_research_dir ): float {
	$output = shell_exec(
		sprintf(
			'cd %s && npm run --silent research benchmark-web-vitals -- -u %s -n %s -o csv',
			escapeshellarg( $wpp_research_dir ),
			escapeshellarg( $url ),
			escapeshellarg( $request_number )
		)
	);

	$lines = preg_split( "/\n/", trim( $output ) );

	if ( count( $lines ) !== 6 ) {
		throw new Exception( STDERR, "Unexpected line count:\n{$output}\n" );
	}

	if ( 'Success Rate,100%' !== $lines[1] ) {
		throw new Exception( STDERR, "Success rate not 100%:\n{$output}\n" );
	}

	if ( ! preg_match( '/^LCP-TTFB.+?,(\d.+)/', $lines[5], $matches ) ) {
		throw new Exception( STDERR, "Cannot find LCP-TTFB:\n{$output}\n" );
	}

	return floatval( $matches[1] );
}