Ignore files when calculating Code Coverage in Xcode

Question

I have recently add some extensions to my app, an example of which can be found below.

Prior to this I was maintaining approx 93% code coverage, this has now dropped to around 56% and it appears all of the extensions I have added are showing 0% coverage.

Whilst I know a high code coverage % is not a gold seal, I do take some confidence in having a higher number.

Is it possible to mark these extensions as to be ignore when calculating %?

If not, is testing these as simple as invoking them within a test case and asserting the results?

I'd rather not test for the sake of testing, eg I don't want to test UIKit as I expect this has happened at Apple.

extension UIStackView {
    func removeAllArrangedSubviews() {
        let removedSubviews = arrangedSubviews.reduce([]) { (allSubviews, subview) -> [UIView] in
            self.removeArrangedSubview(subview)
            return allSubviews + [subview]
        }
        NSLayoutConstraint.deactivate(removedSubviews.flatMap({ $0.constraints }))
        removedSubviews.forEach({ $0.removeFromSuperview() })
    }
}