### Question:
FlowStartEvent extends Event { @Override public void trigger() { transportLayer.startFlow(targetId, flowSizeByte); } FlowStartEvent(long timeFromNowNs, TransportLayer transportLayer, int targetId, long flowSizeByte); @Override void trigger();  }### Answer:
@Test public void testTriggerIsolated() { TransportLayer transportLayer = mock(TransportLayer.class); FlowStartEvent event = new FlowStartEvent(1000, transportLayer, 98, 100000); event.trigger(); verify(transportLayer, times(1)).startFlow(98, 100000); }