We intend to replace PULUMI_TEST_MODE with better testing support
that doesn't suffer from all the pitfalls of our current approach.
Unfortunately, we don't yet have complete guidance or validation
that the new approaches will work for all existing end users. So,
until we do, we'll take a lighter touch approach here, and simply
not encourage new usage of PULUMI_TEST_MODE.
Issue #3045 will remain open to track a mroe permanent fix.
* Enable unit testing for Pulumi programs
This change enables rudimentary unit testing of your Pulumi programs, by introducing a `PULUMI_TEST_MODE` envvar that, when set, allows programs to run without a CLI. That includes
* Just being able to import your Pulumi modules, and test ordinary functions -- which otherwise would have often accidentally triggered the "Not Running in a CLI" error message
* Being able to verify a subset of resource properties and shapes, with the caveat that outputs are not included, due to the fact that this is a perpetual "dry run" without any engine operations occurring
In principle, this also means you can attach a debugger and step through your code.
* Finish the unit testing features
This change
1) Incorporates CR feedback, namely requiring that test mode be
explicitly enabled for any of this to work.
2) Implements Python support for the same capabilities.
3) Includes tests for both JavaScript and Python SDKs.
* Add a note on unit testing to the CHANGELOG
* Use Node 8 friendly assert API
* Embellish the CHANGELOG entry a bit
