onClose not executed on v6.0.4

[AdrienLemaire]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
onOpen works.
onClose doesn't.

What is the expected behavior?
onClose callback should be executed when the toast closes

[fkhadra]

The issue seems related to the new version of react-transition-group. My tests didn't catch it because react-transition-group is mocked. Thanks for reporting the issue