public function testIsLeaf()
 {
     $this->assertTrue($this->categories('Child 1')->isLeaf());
     $this->assertTrue($this->categories('Child 2.1')->isLeaf());
     $this->assertTrue($this->categories('Child 3')->isLeaf());
     $this->assertTrue($this->categories('Root 2')->isLeaf());
     $this->assertFalse($this->categories('Root 1')->isLeaf());
     $this->assertFalse($this->categories('Child 2')->isLeaf());
     $new = new Category();
     $this->assertFalse($new->isLeaf());
 }