@Test
public void testTopOrder() {

    Source src1 = new StreamlineSource(Collections.singleton(new Stream("f1", "f2")));
    Source src2 = new StreamlineSource(Collections.singleton(new Stream("f1", "f2")));
    Sink sink = new StreamlineSink();
    Processor processor = new StreamlineProcessor(Collections.singleton(new Stream("r1")));
    topology.add(src1).add(src2).add(processor).add(sink);
    topology.addEdge(src1, processor);
    topology.addEdge(src2, processor);
    topology.addEdge(processor, sink);
    List<Component> topOrder = topology.topOrder();
    assertArrayEquals(new Component[] {src2, src1, processor, sink}, topOrder.toArray());
}