Add CLI end-to-end tests

[V0ldek]

Is your feature request related to a problem? Please describe.
We need tests for the overall CLI interface to guard against breaking changes (and also E2E test the app).

Describe the solution you'd like
First, a tool needs to be chosen. There's quite a few of them for CLI testing, snapshot testing, etc.

Then tests for each possible parameter configuration need to be created. The files processed should be small, these are not stress tests of the engine but rather E2E tests for the integrity of the entire system.

Additional context
There's a list of possible tools to use in trycmd docs.

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