update

src/main/java/com/zipcoder/payment/Check.java

     }
 
     public int compareTo(Payment o) {
-
-        return 0;
+        int n = this.getShortDescription().compareTo(o.getShortDescription());
+        return n;
     }
 }

src/test/java/com/zipcoder/payment/CheckTest.java

 public class CheckTest {
 
     Check check;
+
     @Before
     public void start(){
         check = new Check(12312l, "Jo","33775", "8800");
     }
 
     @Test
-    public void compareTo() {
-        Check check1 = new Check();
+    public void compareToWhenEquals() {
+            Check check1 = new Check(123l,"Jo","12345","2233");
+            Check check2 = new Check(123l,"Jo","12345","2233");
+            Assert.assertTrue(check1.getShortDescription().compareTo(check2.getShortDescription())==0);
+
+    }
+
+    @Test
+    public void compareToWhenPayment1ComesBeforePayment2() {
+        Check check1 = new Check(123l,"Bo","12345","2233");
+        Check check2 = new Check(222l,"Jo","11345","2233");
+
+        Assert.assertTrue(check1.getShortDescription().compareTo(check2.getShortDescription()) < 0);
+
+    }
+    @Test
+    public void compareToWhenPayment2ComesBeforePayment1() {
+        Check check1 = new Check(123l,"Jo","12345","2233");
+        Check check2 = new Check(122l,"Bo","11345","2233");
+
+        Assert.assertTrue(check1.getShortDescription().compareTo(check2.getShortDescription()) > 0);
+
+    }
+
 
     }
-}