This doesn‘t have all of the features of the product-bundle command (doesn’t talk to the target device, for example), it's helpful to have a more rapid development cycle, since this builds faster.
If/when the build time of the ffx tool is faster, this tool can be removed.
This tool is intended for rapid development only. It is not intended to replace an ffx sub-command.
When working on product_test_tool, consider using:
$ fx set [...] --with-host //src/developer/ffx/lib/pbms/test
Unit tests can be run with:
$ fx test product_test_tool_bin_test