feat(cipher/transposition): add fuzz test to transposition cipher #600

cipher/transposition/transposition.go

@@ -8,19 +8,16 @@
 package transposition
 
 import (
+	"errors"
+	"fmt"
 	"sort"
 	"strings"
 )
 
-type NoTextToEncryptError struct{}
-type KeyMissingError struct{}
+var ErrNoTextToEncrypt = errors.New("no text to encrypt")
+var ErrKeyMissing = errors.New("missing Key")
 
-func (n *NoTextToEncryptError) Error() string {
-	return "No text to encrypt"
-}
-func (n *KeyMissingError) Error() string {
-	return "Missing Key"
-}
+const placeholder = ' '
 
 func getKey(keyWord string) []int {
 	keyWord = strings.ToLower(keyWord)
@@ -51,56 +48,58 @@ func getIndex(wordSet []rune, subString rune) int {
 	return 0
 }
 
-func Encrypt(text []rune, keyWord string) (string, error) {
+func Encrypt(text []rune, keyWord string) ([]rune, error) {
 	key := getKey(keyWord)
-	space := ' '
 	keyLength := len(key)
 	textLength := len(text)
 	if keyLength <= 0 {
-		return "", &KeyMissingError{}
+		return nil, ErrKeyMissing
 	}
 	if textLength <= 0 {
-		return "", &NoTextToEncryptError{}
+		return nil, ErrNoTextToEncrypt
+	}
+	if text[len(text)-1] == placeholder {
+		return nil, fmt.Errorf("%w: cannot encrypt a text, %q, ending with the placeholder char %q", ErrNoTextToEncrypt, text, placeholder)
 	}
 	n := textLength % keyLength
 
 	for i := 0; i < keyLength-n; i++ {
-		text = append(text, space)
+		text = append(text, placeholder)
 	}
 	textLength = len(text)
-	result := ""
+	var result []rune
 	for i := 0; i < textLength; i += keyLength {
 		transposition := make([]rune, keyLength)
 		for j := 0; j < keyLength; j++ {
 			transposition[key[j]-1] = text[i+j]
 		}
-		result += string(transposition)
+		result = append(result, transposition...)
 	}
 	return result, nil
 }
 
-func Decrypt(text []rune, keyWord string) (string, error) {
+func Decrypt(text []rune, keyWord string) ([]rune, error) {
 	key := getKey(keyWord)
 	textLength := len(text)
 	if textLength <= 0 {
-		return "", &NoTextToEncryptError{}
+		return nil, ErrNoTextToEncrypt
 	}
 	keyLength := len(key)
 	if keyLength <= 0 {
-		return "", &KeyMissingError{}
+		return nil, ErrKeyMissing
 	}
-	space := ' '
 	n := textLength % keyLength
 	for i := 0; i < keyLength-n; i++ {
-		text = append(text, space)
+		text = append(text, placeholder)
 	}
-	result := ""
+	var result []rune
 	for i := 0; i < textLength; i += keyLength {
 		transposition := make([]rune, keyLength)
 		for j := 0; j < keyLength; j++ {
 			transposition[j] = text[i+key[j]-1]
 		}
-		result += string(transposition)
+		result = append(result, transposition...)
 	}
+	result = []rune(strings.TrimRight(string(result), string(placeholder)))
 	return result, nil
 }

cipher/transposition/transposition_test.go

@@ -8,20 +8,18 @@ package transposition
 import (
 	"errors"
 	"math/rand"
-	"strings"
+	"reflect"
 	"testing"
 )
 
-const enAlphabet = "abcdefghijklmnopqrstuvwxyz "
+const enAlphabet = "abcdefghijklmnopqrstuvwxyz"
 
-func getTexts() []string {
-	return []string{
-		"Ilya Sokolov",
-		"A slice literal is declared just like an array literal, except you leave out the element count",
-		"Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.",
-		"Go’s treatment of errors as values has served us well over the last decade. Although the standard library’s support for errors has been minimal—just the errors.New and fmt.Errorf functions, which produce errors that contain only a message—the built-in error interface allows Go programmers to add whatever information they desire. All it requires is a type that implements an Error method:",
-		"А тут для примера русский текст",
-	}
+var texts = []string{
+	"Ilya Sokolov",
+	"A slice literal is declared just like an array literal, except you leave out the element count",
+	"Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.",
+	"Go’s treatment of errors as values has served us well over the last decade. Although the standard library’s support for errors has been minimal—just the errors.New and fmt.Errorf functions, which produce errors that contain only a message—the built-in error interface allows Go programmers to add whatever information they desire. All it requires is a type that implements an Error method:",
+	"А тут для примера русский текст",
 }
 
 func getRandomString() string {
@@ -36,12 +34,12 @@ func getRandomString() string {
 func TestEncrypt(t *testing.T) {
 	fn := func(text string, keyWord string) (bool, error) {
 		encrypt, err := Encrypt([]rune(text), keyWord)
-		if err != nil && !errors.Is(err, &NoTextToEncryptError{}) && !errors.Is(err, &KeyMissingError{}) {
+		if err != nil && !errors.Is(err, ErrNoTextToEncrypt) && !errors.Is(err, ErrKeyMissing) {
 			t.Error("Unexpected error ", err)
 		}
-		return text == encrypt, err
+		return text == string(encrypt), err
 	}
-	for _, s := range getTexts() {
+	for _, s := range texts {
 		if check, err := fn(s, getRandomString()); check || err != nil {
 			t.Error("String ", s, " not encrypted")
 		}
@@ -52,52 +50,84 @@ func TestEncrypt(t *testing.T) {
 }
 
 func TestDecrypt(t *testing.T) {
-	for _, s := range getTexts() {
+	for _, s := range texts {
 		keyWord := getRandomString()
 		encrypt, errEncrypt := Encrypt([]rune(s), keyWord)
 		if errEncrypt != nil &&
-			!errors.Is(errEncrypt, &NoTextToEncryptError{}) &&
-			!errors.Is(errEncrypt, &KeyMissingError{}) {
+			!errors.Is(errEncrypt, ErrNoTextToEncrypt) &&
+			!errors.Is(errEncrypt, ErrKeyMissing) {
 			t.Error("Unexpected error ", errEncrypt)
 		}
 		if errEncrypt != nil {
 			t.Error(errEncrypt)
 		}
 		decrypt, errDecrypt := Decrypt([]rune(encrypt), keyWord)
 		if errDecrypt != nil &&
-			!errors.Is(errDecrypt, &NoTextToEncryptError{}) &&
-			!errors.Is(errDecrypt, &KeyMissingError{}) {
+			!errors.Is(errDecrypt, ErrNoTextToEncrypt) &&
+			!errors.Is(errDecrypt, ErrKeyMissing) {
 			t.Error("Unexpected error ", errDecrypt)
 		}
 		if errDecrypt != nil {
 			t.Error(errDecrypt)
 		}
-		if encrypt == decrypt {
+		if reflect.DeepEqual(encrypt, decrypt) {
 			t.Error("String ", s, " not encrypted")
 		}
-		if encrypt == s {
+		if reflect.DeepEqual(encrypt, s) {
 			t.Error("String ", s, " not encrypted")
 		}
 	}
 }
 
 func TestEncryptDecrypt(t *testing.T) {
-	text := "Test text for checking the algorithm"
+	text := []rune("Test text for checking the algorithm")
 	key1 := "testKey"
 	key2 := "Test Key2"
-	encrypt, errEncrypt := Encrypt([]rune(text), key1)
+	encrypt, errEncrypt := Encrypt(text, key1)
 	if errEncrypt != nil {
 		t.Error(errEncrypt)
 	}
-	decrypt, errDecrypt := Decrypt([]rune(encrypt), key1)
+	decrypt, errDecrypt := Decrypt(encrypt, key1)
 	if errDecrypt != nil {
 		t.Error(errDecrypt)
 	}
-	if strings.Contains(decrypt, text) == false {
-		t.Error("The string was not decrypted correctly")
+	if !reflect.DeepEqual(decrypt, text) {
+		t.Errorf("The string was not decrypted correctly %q %q", decrypt, text)
 	}
 	decrypt, _ = Decrypt([]rune(encrypt), key2)
-	if strings.Contains(decrypt, text) == true {
-		t.Error("The string was decrypted with a different key")
+	if reflect.DeepEqual(decrypt, text) {
+		t.Errorf("The string was decrypted with a different key: %q %q", decrypt, text)
+	}
+}
+
+func FuzzTransposition(f *testing.F) {
+	for _, transpositionTestInput := range texts {
+		f.Add(transpositionTestInput)
 	}
+	f.Fuzz(func(t *testing.T, input string) {
+		keyword := getRandomString()
+		message := []rune(input)
+		encrypted, err := Encrypt(message, keyword)
+		switch {
+		case err == nil:
+		case errors.Is(err, ErrKeyMissing),
+			errors.Is(err, ErrNoTextToEncrypt):
+			return
+		default:
+			t.Fatalf("unexpected error when encrypting string %q: %v", input, err)
+		}
+		decrypted, err := Decrypt([]rune(encrypted), keyword)
+		switch {
+		case err == nil:
+		case errors.Is(err, ErrKeyMissing),
+			errors.Is(err, ErrNoTextToEncrypt):
+			return
+		default:
+			t.Fatalf("unexpected error when decrypting string %q: %v", encrypted, err)
+		}
+
+		if !reflect.DeepEqual(message, decrypted) {
+			t.Fatalf("expected: %+v, got: %+v", message, []rune(decrypted))
+		}
+	})
 }