public function testParentRelationRefersToCorrectField()
 {
     $category = new Category();
     $this->assertEquals($category->getParentColumnName(), $category->parent()->getForeignKey());
     $this->assertEquals($category->getQualifiedParentColumnName(), $category->parent()->getQualifiedForeignKey());
 }
 public function testNullifyParentColumnOnNewNodes()
 {
     $node = new Category(['name' => 'Root 3']);
     $node->parent_id = null;
     $node->save();
     $node->reload();
     $this->assertNull($node->parent()->first());
     $this->assertEquals(0, $node->getLevel());
     $this->assertEquals(13, $node->getLeft());
     $this->assertEquals(14, $node->getRight());
     $this->assertTrue(Category::isValidNestedSet());
 }