Erlymock will erase code coverage statistics for a module when it is mocked. This potentially under reports coverage when a test suite is run.

Example

x_tests:test().

Module x has 100% coverage.

y_tests:test() -> 
erlymock:stub(x,foo,[]), 
%...

Module x now has 0% coverage. Reverse the order of x_tests and y_tests, and module x will have 100% coverage.

Problem

In erlymock.erl, load_module runs code:delete and code:purge on the mocked module before inserting the mocked version. This removes the code coverage information. In erlymock:terminate, the mocked code is then deleted and purged, then cover:compiled. This keeps cover from spewing angry messages about code that's not cover compiled, and has no effect if cover is not being used.

Potential fixes

Roughly in order of desirability:

• Can we save a reference to the module and put it back during terminate, rather than delete/purge?
• Is there a way to preserve cover information for the module and reinsert it?