String renderInstructionForDisplay(Instruction instr) {

        // special handling for Extension Instruction Wrappers...
        if (instr instanceof Instructions.ExtensionInstructionWrapper) {
            Instructions.ExtensionInstructionWrapper wrap =
                    (Instructions.ExtensionInstructionWrapper) instr;
            return wrap.type() + COLON + wrap.extensionInstruction();
        }

        // special handling of other instruction classes could be placed here

        // default to the natural string representation otherwise
        return instr.toString();
    }
@Test
    public void renderOutputInstruction() {
        title("renderOutputInstruction");
        instr = Instructions.createOutput(portNumber(4));
        string = instr.toString();
        render = handler.renderInstructionForDisplay(instr);

        print(string);
        assertEquals("not same output", string, render);
        assertEquals("not output to port 4", "OUTPUT:4", render);
    }