Crypto/src/ROT13.java

     ROT13() {
     }
 
-
     public String crypt(String text) throws UnsupportedOperationException {
-
-        return "";
+        StringBuilder builder = new StringBuilder();
+        for (int i = 0; i < text.length(); i++) {
+            char c = text.charAt(i);
+            if(c>='a' && c<= 'm') c+= 13;
+            else if(c >= 'A' && c <='M') c+=13;
+            else if (c >= 'n' && c<= 'z') c-= 13;
+            else if(c >= 'N' && c <= 'Z') c -= 13;
+            builder.append(c);
+        }
+        return builder.toString();
     }
 
     public String encrypt(String text) {
-        return text;
+
+        return crypt(text);
     }
 
     public String decrypt(String text) {
-        return text;
+
+        return crypt(text);
     }
 
     public static String rotate(String s, Character c) {
 
-        return "";
+        int index = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if(s.charAt(i)==(c)){
+                index = i;
+            }
+        }
+        StringBuilder builder = new StringBuilder();
+        for (int i = index; i < s.length(); i++) {
+            builder.append(s.charAt(i));
+        }
+        for (int i = 0; i < index ; i++) {
+            builder.append(s.charAt(i));
+        }
+        return builder.toString();
     }
 
 }

Crypto/src/ROT13Test.java

-import org.junit.Test;
 
-import static org.junit.Assert.*;
+import org.junit.Assert;
+import org.junit.Test;
 
 public class ROT13Test {
 
         String actual = cipher.rotate(s1, 'A');
 
         // Then
-        assertTrue(actual.equals(s2));
+        Assert.assertTrue(actual.equals(s2));
     }
 
     @Test
         String actual = cipher.rotate(s1, 'D');
 
         // Then
-        assertTrue(actual.equals(s2));
+        Assert.assertTrue(actual.equals(s2));
     }
 
     @Test
         System.out.println(s1);
         System.out.println(actual);
         // Then
-        assertTrue(actual.equals(s2));
+        Assert.assertTrue(actual.equals(s2));
     }
 
     @Test
         System.out.println(Q1);
         System.out.println(A1);
         // Then
-        assertTrue(actual.equals(A1));
+        Assert.assertTrue(actual.equals(A1));
 
         // When
         String actual2 = cipher.decrypt(Q2);
         System.out.println(Q2);
         System.out.println(A2);
         // Then
-        assertTrue(actual2.equals(A2));
+        Assert.assertTrue(actual2.equals(A2));
     }
     @Test
     public void cryptTest2() {
         String actual = cipher.crypt(cipher.crypt(Q1));
         System.out.println(actual);
         // Then
-        assertTrue(actual.equals(Q1));
+        Assert.assertTrue(actual.equals(Q1));
     }
 
 }

SimpleCrypt.iml

+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_5">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/Crypto/src" isTestSource="false" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="Maven: junit:junit:4.12" level="project" />
+    <orderEntry type="library" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
+  </component>
+</module>

pom.xml

     <artifactId>SimpleCrypt</artifactId>
     <version>1.0-SNAPSHOT</version>
 
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+        </dependency>
+    </dependencies>
 
 </project>