COLLECTIONS-699 more unit tests

unit tests for equals and toString of the dto entry

src/test/java/org/apache/commons/collections4/iterators/PairingIteratorTest.java

@@ -220,6 +220,36 @@ public class PairingIteratorTest extends AbstractIteratorTest<Entry<String, Stri
         Assert.assertEquals(entry1, entry1);
     }
     
+    @Test
+    public void testEntryEquals_null() {
+        final String firstValue = "A";
+        final String secondValue = "A";
+        final Entry<String, String> entry1 = new Entry<>(firstValue, secondValue);
+
+        Assert.assertNotEquals(entry1, null);
+    }
+    
+    @Test
+    public void testEntryEquals_differentClasses() {
+        final String firstValue = "A";
+        final String secondValue = "A";
+        final Entry<String, String> entry1 = new Entry<>(firstValue, secondValue);
+        
+        Assert.assertNotEquals(entry1, "");
+    }
+    
+    @Test
+    public void testEntryToString() {
+        final String firstValue = "A";
+        final String secondValue = "A";
+        final Entry<String, String> entry = new Entry<>(firstValue, secondValue);
+        
+        String string = entry.toString();
+        Assert.assertTrue(string.contains(firstValue));
+        Assert.assertTrue(string.contains(secondValue));
+        
+    }
+
     @Override
     public Iterator<Entry<String, String>> makeEmptyIterator() {
         return new PairingIterator<String, String>(IteratorUtils.<String>emptyIterator(),