### Question:
IdIndexChangeListener implements ChangeListener { @Override public void onEdgeUpdate(Collection collection, Edge oldEdge, Edge newEdge) { indexHandler.upsertIntoEdgeIdIndex(UUID.fromString(newEdge.value("tim_id")), newEdge); } IdIndexChangeListener(IndexHandler indexHandler); @Override void onCreate(Collection collection, Vertex vertex); @Override void onPropertyUpdate(Collection collection, Optional<Vertex> oldVertex, Vertex newVertex); @Override void onRemoveFromCollection(Collection collection, Optional<Vertex> oldVertex, Vertex newVertex); @Override void onAddToCollection(Collection collection, Optional<Vertex> oldVertex, Vertex newVertex); @Override void onCreateEdge(Collection collection, Edge edge); @Override void onEdgeUpdate(Collection collection, Edge oldEdge, Edge newEdge);  }### Answer:
@Test public void onEdgeUpdateCallsTheIndexHandler() { UUID timId = UUID.randomUUID(); Edge edge = edgeWithId(timId); Edge nullEdge = null; instance.onEdgeUpdate(NULL_COLLECTION, nullEdge, edge); verify(indexHandler).upsertIntoEdgeIdIndex(timId, edge); }