added test helper method, added testPushThreeElements

src/test/java/MyStackTest.java

@@ -17,6 +17,12 @@ public class MyStackTest {
     public void tearDown() {
     }
 
+    private void pushDummies(int numberOfDummies) {
+        for (int i=0; i<numberOfDummies; i++) {
+            stack.push(new Object());
+        }
+    }
+
     @Test
     public void testEmptyStack() {
         assertEquals(0, stack.size());
@@ -24,7 +30,13 @@ public class MyStackTest {
 
     @Test
     public void testPushOneElement() {
-        stack.push(new Object());
+        pushDummies(1);
         assertEquals(1, stack.size());
     }
+
+    @Test
+    public void testPushThreeElements() {
+        pushDummies(3);
+        assertEquals(3, stack.size());
+    }
 }
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