public function testIsBoolean()
 {
     $boolItem = new Item(true);
     $this->assertTrue($boolItem->isBoolean());
     $intItem = new Item(123);
     $this->assertFalse($intItem->isBoolean());
     $floatItem = new Item(1.2);
     $this->assertFalse($floatItem->isBoolean());
     $stringItem = new Item('a string');
     $this->assertFalse($stringItem->isBoolean());
     $arrayItem = new Item(array('an array'));
     $this->assertFalse($arrayItem->isBoolean());
 }