test: Add boundary tests for isChildOf() method in NestedSetsBehavior class.

composer.json

@@ -15,7 +15,7 @@
     },
     "require-dev": {
         "ext-simplexml": "*",
-        "infection/infection": "^0.27|^0.29",
+        "infection/infection": "^0.27|^0.30",
         "maglnet/composer-require-checker": "^4.1",
         "php-forge/support": "^0.1",
         "phpstan/extension-installer": "^1.4",

tests/NestedSetsBehaviorTest.php

@@ -1388,6 +1388,52 @@ public function testReturnIsChildOfForMultipleTreeNodeUnderVariousAncestors(): v
         );
     }
 
+    public function testIsChildOfReturnsFalseWhenLeftValuesAreEqual(): void
+    {
+        $this->generateFixtureTree();
+
+        $parentNode = Tree::findOne(2);
+        $childNode = Tree::findOne(3);
+
+        self::assertNotNull($parentNode, 'Parent node should exist for boundary testing.');
+        self::assertNotNull($childNode, 'Child node should exist for boundary testing.');
+
+        $originalChildLeft = $childNode->getAttribute('lft');
+
+        $parentLeft = $parentNode->getAttribute('lft');
+        $childNode->setAttribute('lft', $parentLeft);
+
+        self::assertFalse(
+            $childNode->isChildOf($parentNode),
+            'Node should not be child when left values are equal (tests <= condition).'
+        );
+
+        $childNode->setAttribute('lft', $originalChildLeft);
+    }
+
+    public function testIsChildOfReturnsFalseWhenRightValuesAreEqual(): void
+    {
+        $this->generateFixtureTree();
+
+        $parentNode = Tree::findOne(2);
+        $childNode = Tree::findOne(3);
+
+        self::assertNotNull($parentNode, 'Parent node should exist for boundary testing.');
+        self::assertNotNull($childNode, 'Child node should exist for boundary testing.');
+
+        $originalChildRight = $childNode->getAttribute('rgt');
+
+        $parentRight = $parentNode->getAttribute('rgt');
+        $childNode->setAttribute('rgt', $parentRight);
+
+        self::assertFalse(
+            $childNode->isChildOf($parentNode),
+            'Node should not be child when right values are equal (tests >= condition).'
+        );
+
+        $childNode->setAttribute('rgt', $originalChildRight);
+    }
+
     public function testIsLeafReturnsTrueForLeafAndFalseForRoot(): void
     {
         $this->generateFixtureTree();