Add tests for how the decommutator handles problematic raw files #77

Background

At present, the primary end-to-end test verifies that the decommutator produces the same output files between the original script and the current CLI tool.

Description

We should also test what happens when the decommutator is run on bad or corrupted raw files, and make sure that the code fails in the way that we intend it too. That includes making sure that it raises the expected exception, and the file exits with an error code.

To test this, we will need example problematic data files.

Implementation

For the exceptions, we can use pytest.raises().

with pytest.raises(ValueError):
    ...
    # if a ValueError has not been raised, this context manager will fail the test