refactor: Update save logic in NestedSetsBehavior class to refresh node after saving. Add test for left and right attribute adjustment when appending child to root.

src/NestedSetsBehavior.php

@@ -296,7 +296,13 @@ public function appendTo(ActiveRecord $node, bool $runValidation = true, array|n
         $this->operation = self::OPERATION_APPEND_TO;
         $this->node = $node;
 
-        return $this->getOwner()->save($runValidation, $attributes);
+        $result = $this->getOwner()->save($runValidation, $attributes);
+
+        if ($result === true) {
+            $node->refresh();
+        }
+
+        return $result;
     }
 
     /**

tests/NestedSetsBehaviorTest.php

@@ -1720,6 +1720,52 @@ public function testAppendChildNodeToRootCreatesValidTreeStructure(): void
         }
     }
 
+    public function testReturnShiftedLeftRightAttributesWhenChildAppendedToRoot(): void
+    {
+        $this->createDatabase();
+
+        $root = new Tree(['name' => 'Root']);
+
+        $root->makeRoot();
+        $root->refresh();
+
+        $child = new Tree(['name' => 'Child']);
+
+        $child->appendTo($root);
+        $child->refresh();
+
+        self::assertEquals(
+            1,
+            $root->lft,
+            'Root node left value should be \'1\' after \'makeRoot\' and appending a child.',
+        );
+        self::assertEquals(
+            4,
+            $root->rgt,
+            'Root node right value should be \'4\' after \'makeRoot\' and appending a child.',
+        );
+        self::assertEquals(
+            2,
+            $child->lft,
+            'Child node left value should be \'2\' after being appended to the root node.',
+        );
+        self::assertEquals(
+            3,
+            $child->rgt,
+            'Child node right value should be \'3\' after being appended to the root node.',
+        );
+        self::assertNotEquals(
+            0,
+            $child->lft,
+            'Child node left value should not be \'0\' after \'appendTo\' operation.',
+        );
+        self::assertNotEquals(
+            1,
+            $child->rgt,
+            'Child node right value should not be \'1\' after \'appendTo\' operation.',
+        );
+    }
+
     public function testThrowExceptionWhenAppendToParentWithNullRightValue(): void
     {
         $this->createDatabase();