Mutation Testing Report

[AlexDenisov]

Hi, Marcin!

I am working on a tool for mutation testing, it is called Mull.
In a nutshell, it is a technique that helps to assert how good a test suite is.

Here how it works: you have a test that tests a function. If you introduce a semantic change into the function, then the test should fail. If that is not the case, then either test or function is not good enough.

Recently I made an attempt to bring Swift support just to check whether it works or not. Lots of work needs to be done to make it production ready, but, in general, results are great and promising.

I assessed the quality of your test suite, and I can conclude that it is great. However, I found some issues, which I share below.
Each entry has the following format: list of tests and change. The system expects at least one of the group of tests to fail based on the mutation. Also, I grouped similar mutations together (advanced by 0, precondition).

I hope this helps to improve your great library!

---

Tests:

CryptoSwiftTests.AESTests/testAESEncryptIncremental
CryptoSwiftTests.AESTests/testAESEncryptCFBLong

Diff:

diff --git a/Sources/CryptoSwift/AES.swift b/Sources/CryptoSwift/AES.swift
index 3574cad..827c03d 100644
--- a/Sources/CryptoSwift/AES.swift
+++ b/Sources/CryptoSwift/AES.swift
@@ -108,7 +108,7 @@ public final class AES: BlockCipher {
     /// - throws: AES.Error
     ///
     /// - returns: Instance
-    public init(key: Array<UInt8>, iv: Array<UInt8>? = nil, blockMode: BlockMode = .CBC, padding: Padding = PKCS7()) throws {
+    public init(key: Array<UInt8>, iv: Array<UInt8>? = nil, blockMode: BlockMode = .CBC, padding: Padding = ZeroPadding()) throws {
         self.key = Key(bytes: key)
         self.blockMode = blockMode
         self.padding = padding

---

Tests:

CryptoSwiftTests.PaddingTests/testPKCS7_0
CryptoSwiftTests.PaddingTests/testPKCS7_1
CryptoSwiftTests.PaddingTests/testPKCS7_2

Diff:

diff --git a/Sources/CryptoSwift/PKCS7.swift b/Sources/CryptoSwift/PKCS7.swift
index 1ccac59..f762e9c 100644
--- a/Sources/CryptoSwift/PKCS7.swift
+++ b/Sources/CryptoSwift/PKCS7.swift
@@ -23,9 +23,9 @@ public struct PKCS7: Padding {
         var withPadding = bytes
         if (padding == 0) {
             // If the original data is a multiple of N bytes, then an extra block of bytes with value N is added.
-            for _ in 0 ..< blockSize {
-                withPadding += [UInt8(blockSize)]
-            }
+//            for _ in 0 ..< blockSize {
+//                withPadding += [UInt8(blockSize)]
+//            }
         } else {
             // The value of each added byte is the number of bytes that are added
             for _ in 0 ..< padding {

---

Tests:

CryptoSwiftTests.PBKDF/testPBKDF2Length
CryptoSwiftTests.HMACTests/testMD5
CryptoSwiftTests.HMACTests/testSHA256
CryptoSwiftTests.HMACTests/testSHA384
CryptoSwiftTests.HMACTests/testSHA512

Diff:

diff --git a/Sources/CryptoSwift/SHA2.swift b/Sources/CryptoSwift/SHA2.swift
index cd60b02..75e8041 100644
--- a/Sources/CryptoSwift/SHA2.swift
+++ b/Sources/CryptoSwift/SHA2.swift
@@ -284,8 +284,6 @@ extension SHA2: Updatable {
                 processedBytes += chunk.count
             }
         }
-        self.accumulated.removeFirst(processedBytes)
-        self.processedBytesTotalCount += processedBytes

         // output current hash
         var result = Array<UInt8>(repeating: 0, count: self.variant.digestLength)

---

Tests:

CryptoSwiftTests.ChaCha20Tests/testChaCha20EncryptPartial
CryptoSwiftTests.ChaCha20Tests/testCore
CryptoSwiftTests.ChaCha20Tests/testVector1Py
CryptoSwiftTests.DigestTests/testSHA1Updatable1
CryptoSwiftTests.DigestTests/testSHA1Updatable2
CryptoSwiftTests.HMACTests/testMD5
CryptoSwiftTests.HMACTests/testSHA256
CryptoSwiftTests.HMACTests/testSHA384
CryptoSwiftTests.HMACTests/testSHA512
CryptoSwiftTests.PBKDF/testPBKDF1
CryptoSwiftTests.PBKDF/testPBKDF2Length
CryptoSwiftTests.RabbitTests/testRabbitWithIV
CryptoSwiftTests.RabbitTests/testRabbitWithoutIV

Diff:

diff --git a/Sources/CryptoSwift/Collection+Extension.swift b/Sources/CryptoSwift/Collection+Extension.swift
index 05217d1..1b25bc8 100644
--- a/Sources/CryptoSwift/Collection+Extension.swift
+++ b/Sources/CryptoSwift/Collection+Extension.swift
@@ -35,7 +35,7 @@ extension Collection where Self.Iterator.Element == UInt8, Self.Index == Int {
             val |= self.count > 3 ? UInt64(self[idx.advanced(by: 3)]) << 24 : 0
             val |= self.count > 2 ? UInt64(self[idx.advanced(by: 2)]) << 16 : 0
             val |= self.count > 1 ? UInt64(self[idx.advanced(by: 1)]) << 8 : 0
-            val |= self.count > 0 ? UInt64(self[idx.advanced(by: 0)]) << 0 : 0
+            val |= self.count > 0 ? UInt64(self[idx]) << 0 : 0
             result.append(val)
         }
 
diff --git a/Sources/CryptoSwift/UInt16+Extension.swift b/Sources/CryptoSwift/UInt16+Extension.swift
index 71f6850..23837a6 100644
--- a/Sources/CryptoSwift/UInt16+Extension.swift
+++ b/Sources/CryptoSwift/UInt16+Extension.swift
@@ -16,7 +16,7 @@ extension UInt16 {
 
     @_specialize(ArraySlice<UInt8>)
     init<T: Collection>(bytes: T, fromIndex index: T.Index) where T.Iterator.Element == UInt8, T.Index == Int {
-        let val0 = UInt16(bytes[index.advanced(by: 0)]) << 8
+        let val0 = UInt16(bytes[index]) << 8
         let val1 = UInt16(bytes[index.advanced(by: 1)])
 
         self = val0 | val1
diff --git a/Sources/CryptoSwift/UInt32+Extension.swift b/Sources/CryptoSwift/UInt32+Extension.swift
index 7c87621..c270248 100644
--- a/Sources/CryptoSwift/UInt32+Extension.swift
+++ b/Sources/CryptoSwift/UInt32+Extension.swift
@@ -25,7 +25,7 @@ extension UInt32 {
 
     @_specialize(ArraySlice<UInt8>)
     init<T: Collection>(bytes: T, fromIndex index: T.Index) where T.Iterator.Element == UInt8, T.Index == Int {
-        let val0 = UInt32(bytes[index.advanced(by: 0)]) << 24
+        let val0 = UInt32(bytes[index]) << 24
         let val1 = UInt32(bytes[index.advanced(by: 1)]) << 16
         let val2 = UInt32(bytes[index.advanced(by: 2)]) << 8
         let val3 = UInt32(bytes[index.advanced(by: 3)])
diff --git a/Sources/CryptoSwift/UInt64+Extension.swift b/Sources/CryptoSwift/UInt64+Extension.swift
index b13f16d..0e2db32 100644
--- a/Sources/CryptoSwift/UInt64+Extension.swift
+++ b/Sources/CryptoSwift/UInt64+Extension.swift
@@ -16,7 +16,7 @@ extension UInt64 {
 
     @_specialize(ArraySlice<UInt8>)
     init<T: Collection>(bytes: T, fromIndex index: T.Index) where T.Iterator.Element == UInt8, T.Index == Int {
-        let val0 = UInt64(bytes[index.advanced(by: 0)]) << 56
+        let val0 = UInt64(bytes[index]) << 56
         let val1 = UInt64(bytes[index.advanced(by: 1)]) << 48
         let val2 = UInt64(bytes[index.advanced(by: 2)]) << 40
         let val3 = UInt64(bytes[index.advanced(by: 3)]) << 32

---

Tests:

CryptoSwiftTests.PBKDF/testPBKDF1
CryptoSwiftTests.PBKDF/testPBKDF2Length
CryptoSwiftTests.DigestTests/testMD5Updates
CryptoSwiftTests.HMACTests/testMD5
CryptoSwiftTests.HMACTests/testSHA256
CryptoSwiftTests.HMACTests/testSHA384
CryptoSwiftTests.HMACTests/testSHA512

Diff:

diff --git a/Sources/CryptoSwift/MD5.swift b/Sources/CryptoSwift/MD5.swift
index df1942f..2588189 100644
--- a/Sources/CryptoSwift/MD5.swift
+++ b/Sources/CryptoSwift/MD5.swift
@@ -8,7 +8,7 @@

 public final class MD5: DigestType {
     static let blockSize: Int = 64
-    static let digestLength: Int = 16 // 128 / 8
+    static let digestLength: Int = 0
     fileprivate static let hashInitialValue: Array<UInt32> = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]

     fileprivate var accumulated = Array<UInt8>()

---

Tests:

CryptoSwiftTests.PBKDF/testPBKDF1
CryptoSwiftTests.PBKDF/testPBKDF2Length
CryptoSwiftTests.DigestTests/testMD5Updates
CryptoSwiftTests.HMACTests/testMD5
CryptoSwiftTests.HMACTests/testSHA256
CryptoSwiftTests.HMACTests/testSHA384
CryptoSwiftTests.HMACTests/testSHA512

Diff:

diff --git a/Sources/CryptoSwift/MD5.swift b/Sources/CryptoSwift/MD5.swift
index 2588189..3e8765e 100644
--- a/Sources/CryptoSwift/MD5.swift
+++ b/Sources/CryptoSwift/MD5.swift
@@ -127,8 +127,6 @@ extension MD5: Updatable {
                 processedBytes += chunk.count
             }
         }
-        self.accumulated.removeFirst(processedBytes)
-        self.processedBytesTotalCount += processedBytes

         // output current hash
         var result = Array<UInt8>()

---

Tests:

CryptoSwiftTests.PBKDF/testPBKDF1
CryptoSwiftTests.PBKDF/testPBKDF2Length
CryptoSwiftTests.ChaCha20Tests/testCore
CryptoSwiftTests.ChaCha20Tests/testVector1Py
CryptoSwiftTests.ChaCha20Tests/testChaCha20EncryptPartial
CryptoSwiftTests.ChaCha20Tests/testChaCha20

Diff:

diff --git a/Sources/CryptoSwift/ChaCha20.swift b/Sources/CryptoSwift/ChaCha20.swift
index 0bc18ba..88794a2 100644
--- a/Sources/CryptoSwift/ChaCha20.swift
+++ b/Sources/CryptoSwift/ChaCha20.swift
@@ -22,8 +22,6 @@ public final class ChaCha20: BlockCipher {
     fileprivate var counter: Array<UInt8>
 
     public init(key: Array<UInt8>, iv nonce: Array<UInt8>) throws {
-        precondition(nonce.count == 12 || nonce.count == 8)
-
         if (key.count != 32) {
             throw Error.invalidKeyOrInitializationVector
         }
@@ -41,9 +39,6 @@ public final class ChaCha20: BlockCipher {
 
     /// https://tools.ietf.org/html/rfc7539#section-2.3.
     fileprivate func core(block: inout Array<UInt8>, counter: Array<UInt8>, key: Array<UInt8>) {
-        precondition(block.count == ChaCha20.blockSize)
-        precondition(counter.count == 16)
-        precondition(key.count == 32)
 
         let j0: UInt32 = 0x61707865
         let j1: UInt32 = 0x3320646e // 0x3620646e sigma/tau
@@ -201,8 +196,6 @@ public final class ChaCha20: BlockCipher {
 
     // XORKeyStream
     func process(bytes: Array<UInt8>, counter: inout Array<UInt8>, key: Array<UInt8>) -> Array<UInt8> {
-        precondition(counter.count == 16)
-        precondition(key.count == 32)
 
         var block = Array<UInt8>(repeating: 0, count: ChaCha20.blockSize)
         var bytes = bytes //TODO: check bytes[bytes.indices]
diff --git a/Sources/CryptoSwift/PKCS5/PBKDF1.swift b/Sources/CryptoSwift/PKCS5/PBKDF1.swift
index e890860..2f3724d 100644
--- a/Sources/CryptoSwift/PKCS5/PBKDF1.swift
+++ b/Sources/CryptoSwift/PKCS5/PBKDF1.swift
@@ -53,8 +53,6 @@ public extension PKCS5 {
         ///   - iterations: iteration count, a positive integer
         ///   - keyLength: intended length of derived key
         public init(password: Array<UInt8>, salt: Array<UInt8>, variant: Variant = .sha1, iterations: Int = 4096 /* c */ , keyLength: Int? = nil /* dkLen */ ) throws {
-            precondition(iterations > 0)
-            precondition(salt.count == 8)
 
             let keyLength = keyLength ?? variant.size
 
diff --git a/Sources/CryptoSwift/PKCS5/PBKDF2.swift b/Sources/CryptoSwift/PKCS5/PBKDF2.swift
index 3a0d817..42c7beb 100644
--- a/Sources/CryptoSwift/PKCS5/PBKDF2.swift
+++ b/Sources/CryptoSwift/PKCS5/PBKDF2.swift
@@ -39,7 +39,6 @@ public extension PKCS5 {
         ///   - iterations: iteration count, a positive integer
         ///   - keyLength: intended length of derived key
         public init(password: Array<UInt8>, salt: Array<UInt8>, iterations: Int = 4096 /* c */ , keyLength: Int? = nil /* dkLen */ , variant: HMAC.Variant = .sha256) throws {
-            precondition(iterations > 0)
 
             let prf = HMAC(key: password, variant: variant)