YAML files such as services.yml located in eZ/Bundle/EzPublishCoreBundle/Resources/config/ seems to be invalid for latest version of phpunit 5.x. but it runs perfectly with 4.8.26 version.

Tried with mutliple online validators found, most of them validates the actual services.yml file.

However in Symfony 3, they have already fixed this issue as seen here for example: https://github.com/symfony/symfony-demo/pull/247/files

Furthermore, reading YAML 1.2 specs, the @ character is reserved, therefore is should be quoted.