Add testing infrastructure

Add the testing framework

Add integration test for package

Add integration test for content item (created by local command)

Add integration test for behavior (created by local command)

Start by inspecting the package layout and any existing test configuration, since the issue names no files or entry points. Identify how local commands create the package, content item, and behavior, then establish the testing framework and add integration coverage for each; done means all three scenarios run successfully in the project test suite.

Written by the indexing model from the issue text.