diff -u b/tests/src/FunctionalJavascript/PosFormTest.php b/tests/src/FunctionalJavascript/PosFormTest.php
--- b/tests/src/FunctionalJavascript/PosFormTest.php
+++ b/tests/src/FunctionalJavascript/PosFormTest.php
@@ -227,6 +227,7 @@
     $this->click('input[name="commerce-pos-back-to-order"]');
     // Add one more T-shirt.
     $this->getSession()->getPage()->fillField('order_items[target_id][order_items][1][quantity]', '3');
+    $web_assert->assertWaitOnAjaxRequest();
 
     $web_assert->pageTextContains('Total $119.60');
     $web_assert->pageTextContains('Cash $50.00');