We've started doing test-driven development at my office, and that means writing lots of unit tests.

My current task involves taking a bunch of pre-existing, scattered code and turning it into a module.

There are a lot of built-in calls in the code, and I'm not sure how to tackle them in the unit tests.

For example, for a call like this: 

unlink( $filename );

[download]

I would like to be able to have that call fail on a file that should be there, but isn't...as if someone had deleted the file while the program was running. Or perhaps it exists, but can't be deleted.

I am familiar with Test::MockModule and Test::MockObject and was hoping that there was a module that mocked built-in calls so that I could manipulate them in the same way. So far, my search-fu has failed me and I can not find such a module.

Likely, I am missing an obvious solution. Would someone care to enlighten me?

In reply to Unit testing built-in functions by aijin

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