How do you test certificate pinning with Alamofire?

So I followed Alamofire's instructions on the Read Me regarding their new Server Trust Policy. Got the certificate from the server, added it to my project and implemented the following code in my project:

let serverTrustPolicies: [String: ServerTrustPolicy] = [
        "someserver.withvalidcer.com": .PinCertificates(
            certificates: ServerTrustPolicy.certificatesInBundle(),
            validateCertificateChain: true,
            validateHost: true
        )
    ]

    let manager = Manager(
        configuration: NSURLSessionConfiguration.defaultSessionConfiguration(),
        serverTrustPolicyManager: ServerTrustPolicyManager(policies: serverTrustPolicies)
    )

My question is how do I test this?

I've tried changing my base api url to our test server, which has a different valid certificate, but the api calls are not being rejected. And I have verified that the code is running on the required api calls.

via Chebli Mohamed