Currently, ToolBox uses a design that leverages inner classes to reduce boilerplate overhead in the test header.

However, the design does not fit well with Jigsaw, since all the compilation dependencies for all the Task types now have to be listed in the @modules section, whether the task type will be used in the test or not.

We should refactor ToolBox to reduce the declared module footprint of the client tests -- and update the tests accordingly.