UserDefaults+TestHelpers

import Foundation

extension UserDefaults {

    /// Returns an empty `UserDefaults` instance suitable for unit testing.
    ///
    /// Based on https://www.swiftbysundell.com/posts/the-power-of-userdefaults-in-swift
    ///
    /// - Parameters:
    ///   - functionName: name of the unit test function.
    ///   - pathName: name of the unit test file (can be a full path).
    static func makeEmptyInstance(for functionName: StaticString = #function, inFile fileName: StaticString = #file) -> UserDefaults {
        guard
            let baseFileName = "\(fileName)".split(separator: "/").last?.split(separator: ".").first,
            let testName = "\(functionName)".split(separator: "(").first
        else {
            fatalError("Could not create suite name from functionName '\(functionName)' and fileName '\(fileName)'")
        }

        let suiteName = "com.hacknicity.FTPZones.test.\(baseFileName).\(testName)"

        guard let userDefaults = self.init(suiteName: suiteName) else {
            fatalError("Could not create UserDefaults for suite name \(suiteName)")
        }

        userDefaults.removePersistentDomain(forName: suiteName)

        return userDefaults
    }
}