I have been trying to add unit tests to an app I've been working on, but when I try to add them for the following extension, I am getting 'resized' is inaccessible due to 'internal' protection level, and as such the unit tests are worthless. (I have simplified to only one function in this example).

import Foundation
import UIKit

extension UIImage {
    func resized(withPercentage percentage: CGFloat) -> UIImage? {
        let canvasSize = CGSize(width: size.width * percentage, height: size.height * percentage)
        UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
        defer { UIGraphicsEndImageContext() }
        draw(in: CGRect(origin: .zero, size: canvasSize))
        return UIGraphicsGetImageFromCurrentImageContext()
    }

    enum JPEGQuality: CGFloat {
        case lowest  = 0
        case low     = 0.25
        case medium  = 0.5
        case high    = 0.75
        case highest = 1
    }

    /// Returns the data for the specified image in JPEG format.
    /// If the image object’s underlying image data has been purged,
    /// calling this function forces that data to be reloaded into memory.
    /// - returns: A data object containing the JPEG data, or nil if there was a problem generating the data.
    /// This function may return nil if the image has no data or if the underlying CGImageRef contains data in an
    /// unsupported bitmap format.
    func jpeg(_ jpegQuality: JPEGQuality) -> Data? {
        return jpegData(compressionQuality: jpegQuality.rawValue)
    }
}

and here's the test

     func testResizedWithPercentage() {
        let image = UIImage(named: "frontImage")!
        let resizedImage = image.resized(withPercentage: 0.5)
        XCTAssertEqual(resizedImage?.size.width, image.size.width * 0.5)
        XCTAssertEqual(resizedImage?.size.height, image.size.height * 0.5)
    }

Thanks @NigelGee that did it..