how can i get the ServerTrustPolicy.certificatesInBundle of alamofire in Unit Testing case in swift?

i use alamofire framework with a project testing.

In a simple project, i can get the list of certificat server by calling ServerTrustPolicy.certificatesInBundle of alamofire.

But how can i do that in project testing ? the ServerTrustPolicy.certificatesInBundle always return me 0 certificat.