Done

Crypto/src/FileEncryptTest.java

+import org.testng.annotations.Test;
+
+import java.io.FileNotFoundException;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertTrue;
+
+public class FileEncryptTest {
+
+    @Test
+    public void testFileEncrypt() throws FileNotFoundException {
+
+
+        String expected="Funyy V pbzcner gurr gb n fhzzre’f qnl?\n" +
+                "Gubh neg zber ybiryl naq zber grzcrengr:\n" +
+                "Ebhtu jvaqf qb funxr gur qneyvat ohqf bs Znl,\n" +
+                "Naq fhzzre’f yrnfr ungu nyy gbb fubeg n qngr;\n" +
+                "Fbzrgvzr gbb ubg gur rlr bs urnira fuvarf,\n" +
+                "Naq bsgra vf uvf tbyq pbzcyrkvba qvzz'q;\n" +
+                "Naq rirel snve sebz snve fbzrgvzr qrpyvarf,\n" +
+                "Ol punapr be angher’f punatvat pbhefr hagevzz'q;\n" +
+                "Ohg gul rgreany fhzzre funyy abg snqr,\n" +
+                "Abe ybfr cbffrffvba bs gung snve gubh bj’fg;\n" +
+                "Abe funyy qrngu oent gubh jnaqre’fg va uvf funqr,\n" +
+                "Jura va rgreany yvarf gb gvzr gubh tebj’fg:\n" +
+                "   Fb ybat nf zra pna oerngur be rlrf pna frr,\n" +
+                "   Fb ybat yvirf guvf, naq guvf tvirf yvsr gb gurr.";
+
+       String actual=ROT13.encrpttextfile();
+
+        assertEquals(actual, expected);
+
+    }
+
+}

Crypto/src/ROT13.java

+import java.io.File;
+import java.io.FileNotFoundException;
+import java.util.Scanner;
 
 public class ROT13  {
 
     }
 
     ROT13() {
+        this.diff = 13;
     }
 
 
-    public String crypt(String text) throws UnsupportedOperationException {
+    public  String crypt(String text) throws UnsupportedOperationException {
         String str="";
 
         for (int i=0; i<text.length(); i++)
         Integer diff=(int)c-(int)'A';
         return string.substring(diff,string.length())+string.substring(0,diff);
     }
+    public static String encrpttextfile() throws FileNotFoundException {
+        File file=new File("sonnet18.txt");
+        Scanner sc=new Scanner(file);
+        StringBuilder br =new StringBuilder();
+        while(sc.hasNext())
+        {
+            ROT13 rot13=new ROT13();
+            String str=rot13.crypt(sc.nextLine());
+            br.append(str+'\n');
+        }
+        System.out.println(br);
+        return br.toString().trim();
+    }
+
+    public static void main(String[] args) throws FileNotFoundException {
+        encrpttextfile();
+    }
 
 }

Crypto/src/ROT13Test.java

 
         // When
         String actual = cipher.crypt(cipher.crypt(Q1));
-        System.out.println(actual);
+        //System.out.println(actual);
         // Then
         assertTrue(actual.equals(Q1));
     }