Apologies for the delayed response.
The purpose of the Juju charms is to facilitate deployment / testing of Bigtop on clouds or cloud-like environments (such as bare-metal or container-based clusters). As such, the charms are not much more than metadata with some minimal code around the existing Puppet scripts and some minimal code to coordinate the connections to other services. We haven't found it practical so far to unit test that, so have focused on enabling the Bigtop smoke-tests.
In order to test a charm like Pig, you’ll first need to setup Juju. Once that’s done, you can build and test charms in your Juju environment as outlined in bigtop-packages/src/charm/README. For convenience, we've published this charm to the charm store. This means you don’t need to build the Pig charm for yourself in order to test or use it – you can simply deploy directly from the store. For Pig, this means deploying the core hadoop-processing bundle and adding Pig to the deployment, as outlined in the “Usage” section of the Pig charm README. Once deployed, you can see deployment status and run the smoke-test, again noted in the Pig charm README.
I hope this is useful info – your question has us thinking about how to best present Juju Charms to the Bigtop community. Our documentation is admittedly developer-centric, so we’ll be proposing an update to the bigtop-packages/src/charm/README that would be beneficial to people interested in using the charms versus people interested in developing charms. We also wanted to ask about adding this information to the Deployment section of the Wiki; what is the process for submitting changes to the Wiki?