         XCTAssertEqual(testData, decrypted!)
     }
     
+    // Generate a set of random strings, with exponential increase in length
+    // starting from 1 to 2^length
     func generatePerformanceTestData(length: Int = 10) -> [String] {
         func randomAlphaNumericString(length: Int) -> String {
             

    // Measure the performance of encrypting/decrypting 10 strings
    // and then make sure the results are expected
    func testEncryptionDecryptionPerformance() {
        let testData = self.generatePerformanceTestData()
        var results = [(raw: String, encrypted: String?, decrypted: String?)]()
        
        // Measure performance of encrypting & decrypting 10 strings

        
        // Generate a set of ten values that are encrypted and then
        // stored as a tuple (decrypted, encrypted)
        let strings = (0..<length).map { i in
            return randomAlphaNumericString(Int(pow(2.0, Double(i))))
        }
        
        return strings
