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Add unit tests for Caesar cipher (#3665)

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Co-authored-by: Yang Libin <contact@yanglibin.info>
This commit is contained in:
Alexandre Velloso 2022-10-26 02:01:35 +01:00 committed by GitHub
parent 7ef75980d5
commit f8897f166d
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2 changed files with 56 additions and 54 deletions
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63
src/main/java/com/thealgorithms/ciphers/Caesar.java
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@ -1,7 +1,5 @@
package com.thealgorithms.ciphers;
import java.util.Scanner;
/**
* A Java implementation of Caesar Cipher. /It is a type of substitution cipher
* in which each letter in the plaintext is replaced by a letter some fixed
@ -18,7 +16,7 @@ public class Caesar {
*
* @return Encrypted message
*/
public static String encode(String message, int shift) {
public String encode(String message, int shift) {
StringBuilder encoded = new StringBuilder();
shift %= 26;
@ -29,10 +27,10 @@ public class Caesar {
// is in-order latin alphabet
char current = message.charAt(i); // Java law : char + int = char
if (IsCapitalLatinLetter(current)) {
if (isCapitalLatinLetter(current)) {
current += shift;
encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
} else if (isSmallLatinLetter(current)) {
current += shift;
encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
} else {
@ -48,7 +46,7 @@ public class Caesar {
*
* @return message
*/
public static String decode(String encryptedMessage, int shift) {
public String decode(String encryptedMessage, int shift) {
StringBuilder decoded = new StringBuilder();
shift %= 26;
@ -56,10 +54,10 @@ public class Caesar {
final int length = encryptedMessage.length();
for (int i = 0; i < length; i++) {
char current = encryptedMessage.charAt(i);
if (IsCapitalLatinLetter(current)) {
if (isCapitalLatinLetter(current)) {
current -= shift;
decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
} else if (isSmallLatinLetter(current)) {
current -= shift;
decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
} else {
@ -72,21 +70,21 @@ public class Caesar {
/**
* @return true if character is capital Latin letter or false for others
*/
private static boolean IsCapitalLatinLetter(char c) {
private static boolean isCapitalLatinLetter(char c) {
return c >= 'A' && c <= 'Z';
}
/**
* @return true if character is small Latin letter or false for others
*/
private static boolean IsSmallLatinLetter(char c) {
private static boolean isSmallLatinLetter(char c) {
return c >= 'a' && c <= 'z';
}
/**
* @return string array which contains all the possible decoded combination.
*/
public static String[] bruteforce(String encryptedMessage) {
public String[] bruteforce(String encryptedMessage) {
String[] listOfAllTheAnswers = new String[27];
for (int i = 0; i <= 26; i++) {
listOfAllTheAnswers[i] = decode(encryptedMessage, i);
@ -94,47 +92,4 @@ public class Caesar {
return listOfAllTheAnswers;
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int shift = 0;
System.out.println("Please enter the message (Latin Alphabet)");
String message = input.nextLine();
System.out.println(message);
System.out.println("(E)ncode or (D)ecode or (B)ruteforce?");
char choice = input.next().charAt(0);
switch (choice) {
case 'E':
case 'e':
System.out.println("Please enter the shift number");
shift = input.nextInt() % 26;
System.out.println(
"ENCODED MESSAGE IS \n" + encode(message, shift)
); // send our function to handle
break;
case 'D':
case 'd':
System.out.println("Please enter the shift number");
shift = input.nextInt() % 26;
System.out.println(
"DECODED MESSAGE IS \n" + decode(message, shift)
);
break;
case 'B':
case 'b':
String[] listOfAllTheAnswers = bruteforce(message);
for (int i = 0; i <= 26; i++) {
System.out.println(
"FOR SHIFT " +
String.valueOf(i) +
" decoded message is " +
listOfAllTheAnswers[i]
);
}
default:
System.out.println("default case");
}
input.close();
}
}

47
src/test/java/com/thealgorithms/ciphers/CaesarTest.java Normal file
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@ -0,0 +1,47 @@
package com.thealgorithms.ciphers;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
class CaesarTest {
Caesar caesar = new Caesar();
@Test
void caesarEncryptTest() {
// given
String textToEncrypt = "Encrypt this text";
// when
String cipherText = caesar.encode(textToEncrypt, 5);
// then
assertEquals("Jshwduy ymnx yjcy", cipherText);
}
@Test
void caesarDecryptTest() {
// given
String encryptedText = "Jshwduy ymnx yjcy";
// when
String cipherText = caesar.decode(encryptedText, 5);
// then
assertEquals("Encrypt this text", cipherText);
}
@Test
void caesarBruteForce() {
// given
String encryptedText = "Jshwduy ymnx yjcy";
// when
String[] allPossibleAnswers = caesar.bruteforce(encryptedText);
assertEquals(27, allPossibleAnswers.length);
assertEquals("Encrypt this text", allPossibleAnswers[5]);
}
}