add initial HistoryEntry.equals() test

Author: Vladimir Kotal

opengrok-indexer/src/test/java/org/opengrok/indexer/history/HistoryEntryTest.java

@@ -32,6 +32,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -246,4 +247,11 @@ public void strip() {
         assertNull(instance.getTags());
     }
 
+    @Test
+    public void testEquals() {
+        // TODO: add tests with nulls
+        HistoryEntry e = new HistoryEntry(instance);
+        assertNotSame(e, instance);
+        assertEquals(e, instance);
+    }
 }