For such questions, reopen.europa.eu is the best starting point. In general, if you need a test depends on your vaccination status and where you've been in the 10 days before entering Germany. If you're only passing through Germany (max. 24 hours), you don't always need a test.

You will need one for entering Switzerland. And, after few days you need to test again (at this time they also allow antigen rapid test) in Switzerland. If I remember correctly, you even need to go to Quarantine between those two tests if you are not vaccinated or recovered.