### Question:
OperationPipeline implements OperationList { @Override public Operation getTailOperation() { if (operations.size() > 0) { return operations.get(operations.size()-1); } else { return null; } } OperationPipeline(); @Override Operation getTailOperation(); @Override void add(Operation op); @Override OperationIterator iterator();  }### Answer:
@Test public void testOperationPipelineWithNoOperations(){ OperationPipeline operationPipeline = new OperationPipeline(); assertNull(operationPipeline.getTailOperation()); }