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Add unit tests for Caesar cipher (#3665)
Co-authored-by: Yang Libin <contact@yanglibin.info>
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@ -1,7 +1,5 @@
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package com.thealgorithms.ciphers;
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package com.thealgorithms.ciphers;
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import java.util.Scanner;
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/**
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/**
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* A Java implementation of Caesar Cipher. /It is a type of substitution cipher
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* A Java implementation of Caesar Cipher. /It is a type of substitution cipher
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* in which each letter in the plaintext is replaced by a letter some fixed
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* in which each letter in the plaintext is replaced by a letter some fixed
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@ -18,7 +16,7 @@ public class Caesar {
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*
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*
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* @return Encrypted message
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* @return Encrypted message
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*/
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*/
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public static String encode(String message, int shift) {
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public String encode(String message, int shift) {
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StringBuilder encoded = new StringBuilder();
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StringBuilder encoded = new StringBuilder();
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shift %= 26;
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shift %= 26;
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@ -29,10 +27,10 @@ public class Caesar {
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// is in-order latin alphabet
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// is in-order latin alphabet
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char current = message.charAt(i); // Java law : char + int = char
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char current = message.charAt(i); // Java law : char + int = char
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if (IsCapitalLatinLetter(current)) {
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if (isCapitalLatinLetter(current)) {
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current += shift;
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current += shift;
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encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
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encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
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} else if (IsSmallLatinLetter(current)) {
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} else if (isSmallLatinLetter(current)) {
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current += shift;
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current += shift;
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encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
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encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
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} else {
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} else {
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@ -48,7 +46,7 @@ public class Caesar {
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*
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*
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* @return message
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* @return message
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*/
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*/
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public static String decode(String encryptedMessage, int shift) {
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public String decode(String encryptedMessage, int shift) {
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StringBuilder decoded = new StringBuilder();
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StringBuilder decoded = new StringBuilder();
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shift %= 26;
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shift %= 26;
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@ -56,10 +54,10 @@ public class Caesar {
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final int length = encryptedMessage.length();
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final int length = encryptedMessage.length();
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for (int i = 0; i < length; i++) {
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for (int i = 0; i < length; i++) {
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char current = encryptedMessage.charAt(i);
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char current = encryptedMessage.charAt(i);
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if (IsCapitalLatinLetter(current)) {
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if (isCapitalLatinLetter(current)) {
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current -= shift;
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current -= shift;
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decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
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decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
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} else if (IsSmallLatinLetter(current)) {
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} else if (isSmallLatinLetter(current)) {
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current -= shift;
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current -= shift;
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decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
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decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
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} else {
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} else {
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@ -72,21 +70,21 @@ public class Caesar {
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/**
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/**
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* @return true if character is capital Latin letter or false for others
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* @return true if character is capital Latin letter or false for others
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*/
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*/
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private static boolean IsCapitalLatinLetter(char c) {
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private static boolean isCapitalLatinLetter(char c) {
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return c >= 'A' && c <= 'Z';
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return c >= 'A' && c <= 'Z';
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}
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}
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/**
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/**
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* @return true if character is small Latin letter or false for others
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* @return true if character is small Latin letter or false for others
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*/
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*/
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private static boolean IsSmallLatinLetter(char c) {
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private static boolean isSmallLatinLetter(char c) {
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return c >= 'a' && c <= 'z';
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return c >= 'a' && c <= 'z';
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}
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}
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/**
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/**
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* @return string array which contains all the possible decoded combination.
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* @return string array which contains all the possible decoded combination.
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*/
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*/
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public static String[] bruteforce(String encryptedMessage) {
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public String[] bruteforce(String encryptedMessage) {
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String[] listOfAllTheAnswers = new String[27];
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String[] listOfAllTheAnswers = new String[27];
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for (int i = 0; i <= 26; i++) {
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for (int i = 0; i <= 26; i++) {
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listOfAllTheAnswers[i] = decode(encryptedMessage, i);
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listOfAllTheAnswers[i] = decode(encryptedMessage, i);
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@ -94,47 +92,4 @@ public class Caesar {
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return listOfAllTheAnswers;
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return listOfAllTheAnswers;
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}
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}
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public static void main(String[] args) {
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Scanner input = new Scanner(System.in);
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int shift = 0;
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System.out.println("Please enter the message (Latin Alphabet)");
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String message = input.nextLine();
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System.out.println(message);
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System.out.println("(E)ncode or (D)ecode or (B)ruteforce?");
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char choice = input.next().charAt(0);
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switch (choice) {
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case 'E':
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case 'e':
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System.out.println("Please enter the shift number");
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shift = input.nextInt() % 26;
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System.out.println(
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"ENCODED MESSAGE IS \n" + encode(message, shift)
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); // send our function to handle
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break;
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case 'D':
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case 'd':
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System.out.println("Please enter the shift number");
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shift = input.nextInt() % 26;
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System.out.println(
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"DECODED MESSAGE IS \n" + decode(message, shift)
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);
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break;
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case 'B':
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case 'b':
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String[] listOfAllTheAnswers = bruteforce(message);
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for (int i = 0; i <= 26; i++) {
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System.out.println(
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"FOR SHIFT " +
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String.valueOf(i) +
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" decoded message is " +
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listOfAllTheAnswers[i]
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);
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}
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default:
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System.out.println("default case");
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}
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input.close();
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}
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}
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}
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47
src/test/java/com/thealgorithms/ciphers/CaesarTest.java
Normal file
47
src/test/java/com/thealgorithms/ciphers/CaesarTest.java
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@ -0,0 +1,47 @@
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package com.thealgorithms.ciphers;
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import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.*;
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class CaesarTest {
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Caesar caesar = new Caesar();
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@Test
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void caesarEncryptTest() {
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// given
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String textToEncrypt = "Encrypt this text";
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// when
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String cipherText = caesar.encode(textToEncrypt, 5);
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// then
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assertEquals("Jshwduy ymnx yjcy", cipherText);
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}
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@Test
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void caesarDecryptTest() {
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// given
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String encryptedText = "Jshwduy ymnx yjcy";
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// when
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String cipherText = caesar.decode(encryptedText, 5);
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// then
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assertEquals("Encrypt this text", cipherText);
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}
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@Test
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void caesarBruteForce() {
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// given
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String encryptedText = "Jshwduy ymnx yjcy";
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// when
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String[] allPossibleAnswers = caesar.bruteforce(encryptedText);
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assertEquals(27, allPossibleAnswers.length);
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assertEquals("Encrypt this text", allPossibleAnswers[5]);
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}
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}
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