Travis tests were failing with the following error:
```
Expectation failed for method name is equal to <string:mapFormsToData> when invoked 1 time(s)
Parameter 1 for invocation Symfony\Component\Form\DataMapperInterface::mapFormsToData(Array (...), Array ()) does not match expected value.
Array () does not match expected type "object".

/home/travis/build/symfony/symfony/src/Symfony/Component/Form/Form.php:521
/home/travis/build/symfony/symfony/tests/Symfony/Tests/Component/Form/FormTest.php:799
```

If you think this change is wrong, let me know, I'll investigate more.
FYI FormTest works for me too.