+1 to this.

Activity test times out at 10 minute point, which is too short for some of my activities.

If I want to use the test suite to run an activity which takes longer than that, it fails with a timeout error.

While supporting an override is fine, in general I think you should use a real server if you are running such tests (you can easily start a dev server using the testsuite package).

you can easily start a dev server using the testsuite package

Which is extra boilerplate code just to execute an Activity, isn't it?

I already have loads of test Workflows that bloat my project and bring confusion by decoupling the Go's testing tools from those "tests". I end up saving results of those Workflows to a file and then manually check the results instead of implementing testing package.

Which is extra boilerplate code just to execute an Activity, isn't it?

Not sure about "boilerplate". It starts a real server you can do real integration tests on. There's a lot of value in running against a real server.