In belgium anyone with a bogus test certificate will have to appear before a judge and will risk a prison sentence of up to 5 years and a fine of 2,000 euro. In some cases, 750 euro on the spot fines will be issued.
https://www.vrt.be/vrtnws/en/2021/04/27/stiffer-sentences-for-those-caught-travelling-with-fake-coronavi/