testbench output control, stupid question

[Altera_Forum]

Hi to all!  

I have a quite stupid question, I think.  I have a testbench, where I force the output to the right result. If my code works how I expect, the output would be exactly equal to the one I expected, while if my code doesn't work, I will see red X on some parts or on all the output signal in ModelSim.   The stupid question is this: how could I do to have a std_logic signal which tells me the rightness of the output? I mean: for example a signal which is low when the output is right, high when the output goes to X   thank you http://www.edaboard.com/images/smiles/icon_wink.gif

[Altera_Forum]

Are you forcing the output from the testbench or inside the entity? 

 For the answer you want, add this to the testbench: error <= '1' when to_X01(forced_output) = 'X' else '0';  the to_X01 function will mean 'U', 'W', 'Z' and '-' are converted to 'X' too.