@Test
public void testPair() {

  final Pair<Object, Object> objectPair = Pair.of(leftObject, rightObject);
  final Pair<Object, Object> identicalObjectPair = Pair.of(leftObject, rightObject);
  final Pair<IRVertex, IRVertex> irVertexPair = Pair.of(leftSource, rightSource);
  final Pair<Object, IRVertex> mixedPair = Pair.of(leftObject, rightSource);
  assertEquals(leftObject, objectPair.left());
  assertEquals(rightObject, objectPair.right());
  assertEquals(leftSource, irVertexPair.left());
  assertEquals(rightSource, irVertexPair.right());
  assertEquals(leftObject, mixedPair.left());
  assertEquals(rightSource, mixedPair.right());
  assertEquals(objectPair, identicalObjectPair);
}