diff --git a/tests/phpunit/tests/mail.php b/tests/phpunit/tests/mail.php
index 547ed99..d7d5abf 100644
--- a/tests/phpunit/tests/mail.php
+++ b/tests/phpunit/tests/mail.php
@@ -72,6 +72,40 @@ class Tests_Mail extends WP_UnitTestCase {
 	}
 
 	/**
+	 * @ticket 15448
+	 */
+	function test_wp_mail_plain_and_html() {
+		$to = 'user@example.com';
+		$subject = 'Test email with plain text and html versions';
+		$messages = array( 'text/plain' => 'Here is some plain text.',
+					   'text/html' =>'<html><head></head><body>Here is the HTML ;-)<body></html>' );
+
+		wp_mail( $to, $subject, $messages );
+
+		preg_match( '/boundary="(.*)"/', $GLOBALS['phpmailer']->mock_sent[0]['header'], $matches);
+		$boundry = $matches[1];
+		$body = '--' . $boundry . '
+Content-Type: text/plain; charset = "UTF-8"
+Content-Transfer-Encoding: 8bit
+
+Here is some plain text.
+
+
+--' . $boundry . '
+Content-Type: text/html; charset = "UTF-8"
+Content-Transfer-Encoding: 8bit
+
+<html><head></head><body>Here is the HTML ;-)<body></html>
+
+
+
+--' . $boundry . '--
+';
+		// We need some better assertions here but these test the behaviour for now.
+		$this->assertEquals($body, $GLOBALS['phpmailer']->mock_sent[0]['body']);
+	}
+
+	/**
 	 * @ticket 17305
 	 */
 	function test_wp_mail_rfc2822_addresses() {