Question

Is there a way to do unit test for module which does not return anything. My function is a void function and it formats the output and write it to a text file.
I am not sure how do unit testing for such a method.

Any suggestions…
Thanks

Answer 1

Pass in the dependency!

Instead of directly writing to a file, have your method write to a stream instead.

This abstraction allows you to execute the method on a file stream for normal program operation, but for your unit tests you could pass in a memory stream and then verify that the appropriate text has been written to the stream after the method call.

Alternatively you could separate writing to the stream or file from preparing the actual content to write. This would allow you to assert that the correct content is prepared independently from actually writing it out.