If you're going all-in on Google Cloud and using Firestore, then use the emulators [0]. The emulators includes Pub/Sub. For Cloud Task Queues, use an unofficial emulator [1]
If you're not going all-in on Google Cloud and say you want to use Postgres, then use a `docker-compose.yaml` file and pull in a Postgres container instance or run a local Postgres if you want. Then pick a free Postgres compatible cloud service for the actual runtime (e.g. Supabase free tier). Same goes for MySQL.
For AWS, I'd use LocalStack [2]
[0] https://github.com/CharlieDigital/dn6-firebase
Using real resources is usually fine for smaller applications but can be very problematic as your application grows. With that in mind, it's good to create boundaries so you limit the amount of "real infrastructure" you need to test/deploy. Reference https://martinfowler.com/bliki/IntegrationTest.html
You still get assurance from testing but reduce the amount of places you run the "expensive" (time, resource, $) tests