silence network comm of firebase to https://device-provisioning.googleapis.com/checkin

FakeFirebaseInstanceID.swift

final class FakeFirebaseInstanceID: NSObject {
    @objc class func instanceID() -> FakeFirebaseInstanceID? { return nil }

    static private let once: Void = {
        method_exchangeImplementations(
            class_getClassMethod(NSClassFromString("FIRInstanceID"), #selector(FakeFirebaseInstanceID.instanceID))!,
            class_getClassMethod(FakeFirebaseInstanceID.self, #selector(FakeFirebaseInstanceID.instanceID))!)
    }()

    static func silenceFirebaseCheckin() {
        _ = once
    }
}