This plugin inserts additonal buttons into the flexcheckout mask of PostFinance to provide test creditcards. Depending on the brand, a valid card, am invalid card and a card with 3D secure is provided.
Install Link: https://chrome.google.com/webstore/detail/test-creditcards-for-post/ikghmkdkihbhgpfmaaidhobbhfkdhdfp?hl=de
Credits: Lurin, as always