Build out examples/documentation documenting actor unit testing

## Describe the feature
It's not necessarily well-documented how actors should be tested (e.g. lack of specific Mocks). This issue represents an opportunity to address this.

Start by reviewing the repository's existing actor examples and documentation, then examine how actor unit tests are currently structured and where mock guidance is missing. Done means the project contains clear examples and documentation explaining how to test actors, including the relevant mocking approach.

Written by the indexing model from the issue text.