func isValid(testStr:String) -> Bool {
    guard testStr.count > 7, testStr.count < 18 else { return false }

    let predicateTest = NSPredicate(format: "SELF MATCHES %@", "^(([^ ]?)(^[a-zA-Z].*[a-zA-Z]$)([^ ]?))$")
    return predicateTest.evaluate(with: testStr)
}