<form method="POST">
    <h3>Editing: EmailHtmlBodyContains.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mime\Test\Constraint;

use PHPUnit\Framework\Constraint\Constraint;
use Symfony\Component\Mime\Message;
use Symfony\Component\Mime\RawMessage;

final class EmailHtmlBodyContains extends Constraint
{
    private $expectedText;

    public function __construct(string $expectedText)
    {
        $this-&gt;expectedText = $expectedText;
    }

    /**
     * {@inheritdoc}
     */
    public function toString(): string
    {
        return sprintf('contains &quot;%s&quot;', $this-&gt;expectedText);
    }

    /**
     * {@inheritdoc}
     *
     * @param RawMessage $message
     */
    protected function matches($message): bool
    {
        if (RawMessage::class === \get_class($message) || Message::class === \get_class($message)) {
            throw new \LogicException('Unable to test a message HTML body on a RawMessage or Message instance.');
        }

        return false !== mb_strpos($message-&gt;getHtmlBody(), $this-&gt;expectedText);
    }

    /**
     * {@inheritdoc}
     *
     * @param RawMessage $message
     */
    protected function failureDescription($message): string
    {
        return 'the Email HTML body '.$this-&gt;toString();
    }
}
</textarea><br>
    <input type="submit" value="Save">
</form>