public function testUnsetElement()
 {
     $this->_populateSampleStructure();
     // non-recursively
     $this->assertTrue($this->_structure->unsetElement('six', false));
     $this->assertFalse($this->_structure->unsetElement('six', false));
     $this->assertSame([5], $this->_structure->getElement('five'));
     // recursively
     $this->assertTrue($this->_structure->unsetElement('four'));
     $this->assertSame(['one' => [], 'five' => [5]], $this->_structure->exportElements());
 }