An extension on UserDefaults, which’ll enable us to easily create an instance that has had all of its persisted values completely cleared

CleanUserDefaults.swift

extension UserDefaults {
    static func makeClearedInstance(
        for functionName: StaticString = #function,
        inFile fileName: StaticString = #file
    ) -> UserDefaults {
        let className = "\(fileName)".split(separator: ".")[0]
        let testName = "\(functionName)".split(separator: "(")[0]
        let suiteName = "com.johnsundell.test.\(className).\(testName)"

        let defaults = self.init(suiteName: suiteName)!
        defaults.removePersistentDomain(forName: suiteName)
        return defaults
    }
}