lcov report has bad metrics when using sandbox

I tried producing a code coverage report using the lcov reporter. It works as long as I don't mess with the sandbox util.

I'm using the sandbox utility to replace 'require' and mock out modules used by the module under test.

I've been working really hard at trying different code coverage tools and different ways to mock.

Should I be mocking differently or is there a way we could fix the code coverage instrumentation?

Start by reproducing the lcov reporter output with the sandbox utility enabled and disabled, using the module-mocking setup described in the issue. Inspect the lcov reporter and sandbox interaction to determine whether mocking changes instrumentation or only the reported metrics. Done means the report metrics are accurate with sandbox usage, or the supported mocking limitation is clearly established.

Written by the indexing model from the issue text.