Mock out logging and write characterization tests for error scenarios

[Ryan Edwards]

In order to write some verbose characterization tests for this code base we need to be able to have a good way to validate in detail why a file was invalidated. In order to do this we need to figure out the best way to get the output from the log file to assert against. The output for this issue will be the following:

1. Figure out the best way to mock/spy on the logger output
2. Write an assortment of unit tests to verify validation behavior
3. Look into mocking out the input file to facilitate easy manipulation of file content for testing