graphQl-256: added additional check to test

Author: Vitaliy Boyko

dev/tests/api-functional/testsuite/Magento/GraphQl/ConfigurableProduct/ConfigurableProductViewTest.php

@@ -407,6 +407,7 @@ private function assertConfigurableVariants($actualResponse)
                 $variantArray['product']['price']
             );
             $configurableOptions = $this->getConfigurableOptions();
+            $this->assertEquals(1, count($variantArray['attributes']));
             foreach ($variantArray['attributes'] as $attribute) {
                 $hasAssertion = false;
                 foreach ($configurableOptions as $option) {