SetOnActivityHeartbeatListener on TestActivityEnvironment

[cretz]

What was changed

Added SetOnActivityHeartbeatListener on TestActivityEnvironment same as TestWorkflowEnvironment

Why?

Need to be able to mock heartbeat calls to server

Checklist

1. Closes Add TestActivityEnvironment.SetOnActivityHeartbeatListener #768

[bergundy]

What's the added value of this callback over using activity interceptors?

[cretz]

What's the added value of this callback over using activity interceptors?

This is for the testing framework. We already have it for TestWorkflowEnvironment so it's just inconsistent not to have it for TestActivityEnvironment. That we could replace many of our mocks/callbacks with interceptors I think is a different discussion.

[bergundy]

What's the added value of this callback over using activity interceptors?

This is for the testing framework. We already have it for TestWorkflowEnvironment so it's just inconsistent not to have it for TestActivityEnvironment. That we could replace many of our mocks/callbacks with interceptors I think is a different discussion.

Sure, just with interceptors you wouldn't have to add the comment below which of course will come as a surprise to many users.
I'd at least add a sentence stating that interceptors can be used to track each heartbeat call.

// Note: Due to internal caching by the activity system, this may not get called
// for every heartbeat recorded. This is only called when the heartbeat would be
// sent to the server (periodic batch and at the end only on failure).

[cretz]

@bergundy - Added the comment. Agreed the behavior is confusing, but it is already in use that way.