Exception->getCode() is allowed to return mixed.But unfortunately it seems impossible to test against something else than integer exception code because I cannot create such an exception.
This is not allowed: `new \Exception('', 'foo');` and even mocking does not work. phpunit does not use the mocked method. Maybe phpunit bug or its impossible to mock exception completely.

```
$exception = $this->getMock('\Exception');
$exception->expects($this->once())
    ->method('getCode')
    ->will($this->returnValue('foo'));
```