Fix lever responses and add new test for get category by id

Author: nuzil

app/code/Magento/CatalogGraphQl/Model/Resolver/Products/DataProvider/ExtractDataFromCategoryTree.php

@@ -15,8 +15,6 @@
  */
 class ExtractDataFromCategoryTree
 {
-    const START_CATEGORY_FETCH_LEVEL = 1;
-
     /**
      * @var Hydrator
      */
@@ -27,6 +25,11 @@ class ExtractDataFromCategoryTree
      */
     private $iteratingCategory;
 
+    /**
+     * @var int
+     */
+    private $startCategoryFetchLevel = 1;
+
     /**
      * @param Hydrator $categoryHydrator
      */
@@ -51,9 +54,12 @@ public function execute(\Iterator $iterator): array
             $iterator->next();
 
             $pathElements = explode("/", $category->getPath());
-            $this->iteratingCategory = $category;
+            if (empty($tree)){
+                $this->startCategoryFetchLevel = count($pathElements) - 1;
+            }
 
-            $currentLevelTree = $this->explodePathToArray($pathElements, self::START_CATEGORY_FETCH_LEVEL);
+            $this->iteratingCategory = $category;
+            $currentLevelTree = $this->explodePathToArray($pathElements, $this->startCategoryFetchLevel);
             if (empty($tree)) {
                 $tree = $currentLevelTree;
             }

dev/tests/api-functional/testsuite/Magento/GraphQl/Catalog/CategoryTest.php

@@ -112,6 +112,44 @@ public function testCategoriesTree()
         );
     }
 
+    /**
+     * @magentoApiDataFixture Magento/Customer/_files/customer.php
+     * @magentoApiDataFixture Magento/Catalog/_files/categories.php
+     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
+     */
+    public function testGetCategoryById()
+    {
+        $rootCategoryId = 13;
+        $query = <<<QUERY
+{
+  category(id: {$rootCategoryId}) {
+      id
+      name
+  }
+}
+QUERY;
+
+        // get customer ID token
+        /** @var \Magento\Integration\Api\CustomerTokenServiceInterface $customerTokenService */
+        $customerTokenService = $this->objectManager->create(
+            \Magento\Integration\Api\CustomerTokenServiceInterface::class
+        );
+        $customerToken = $customerTokenService->createCustomerAccessToken('customer@example.com', 'password');
+
+        $headerMap = ['Authorization' => 'Bearer ' . $customerToken];
+        $response = $this->graphQlQuery($query, [], '', $headerMap);
+        $responseDataObject = new DataObject($response);
+        //Some sort of smoke testing
+        self::assertEquals(
+            'Category 1.2',
+            $responseDataObject->getData('category/name')
+        );
+        self::assertEquals(
+            13,
+            $responseDataObject->getData('category/id')
+        );
+    }
+
     /**
      * @magentoApiDataFixture Magento/Catalog/_files/categories.php
      * @SuppressWarnings(PHPMD.ExcessiveMethodLength)