public function testGetAllVariables()
 {
     $state = new State();
     $this->assertEquals(0, count($state->getAllVariables()));
     $state->setVariable(new ResponseVariable('RESPONSE1', Cardinality::SINGLE, BaseType::INTEGER, new Integer(25)));
     $this->assertEquals(1, count($state->getAllVariables()));
     $state->setVariable(new OutcomeVariable('SCORE1', Cardinality::SINGLE, BaseType::BOOLEAN, new Boolean(true)));
     $this->assertEquals(2, count($state->getAllVariables()));
     unset($state['RESPONSE1']);
     $this->assertEquals(1, count($state->getAllVariables()));
     $this->assertInstanceOf('qtism\\runtime\\common\\VariableCollection', $state->getAllVariables());
 }