What virus is harmless yet can test an AV scanner?

How many times have you seen the icon for an AV program look fine, see that the program is running, even run a scan and find no viruses/ worms/ trojans only to later determine that the AV scanner was disabled and made to look like it worked when it did not work? Is there an utterly harmless virus that can be placed on a CD or floppy that can be detected by AV scanners as a virus, yet it won’t do anything to the computer?

Thanks in advance.