Create integration tests for our prompt2model_demo.py and .ipynb workflows

[viswavi]

We currently have interfaces to interact with prompt2model, in the form of prompt2model_demo.py and prompt2model_demo.ipynb. While the individual components of prompt2model are generally well-tested, these two files are completely untested.

We need integration tests ASAP to prevent the breaking of these files (such as happened after merging #315 and #344).