feat: adds unit tests for sync and async reads of a pipeline transformation

[kevkim-codes]

Discovered there may be some unit test coverage needed to test pipeline transformations during a Cloud Bigtable feature PR (googleapis/nodejs-bigtable#1494).

[leahecole]

A couple of overall pieces of feedback:

• I think a test should also be added to the test application that does this
• I know our problem before was the test timing out because "done" was never called, but also make sure it's possible for it to fail and to fail LOUDLY :)! It might in its current state, but it might not , which is why I added those notes about "done" and the errors

[kevkim-codes]

A couple of overall pieces of feedback:

• I think a test should also be added to the test application that does this
• I know our problem before was the test timing out because "done" was never called, but also make sure it's possible for it to fail and to fail LOUDLY :)! It might in its current state, but it might not , which is why I added those notes about "done" and the errors

1. Sounds good. I will have a separate PR for the test application.

2. Incorporated your changes in the review and made the error handling better, thank you!

[leahecole]

Just these nits

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• .github/workflows/ci.yaml - .github/workflows/ci.yaml (GitHub Actions) should be updated in synthtool

[leahecole]

Please add the compodoc stuff as a separate pr!

[kevkim-codes]

Please add the compodoc stuff as a separate pr!
Removed!

Change completed