Prompt: Program tests

Your task is to analyze the following python project code files and suggest pytests that should be created and added to the codebase to improve it's testability.

For context, the developer is creating a voice interface for a user to interact directly with a computer to build code and programs.

Where possible, try to relate the functionality suggestions to specific code files.

Do not provide suggestions about the following topics:
- Use of global variables is required for multithreading and will not be altered

Following is the project README, then the code files with code naming headers.
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