Test coverage for structs and mocks

I’m working on a umbrella app that relies on the built-in test coverage tools to generate reports, e.g

mix test --cover --export-coverage default
mix test.coverage

I’m noticing that modules that do nothing other than declare structs and mocked modules (mocked via mox) both show up as 0% coverage in the coverage report. For example:

defmodule Bar do
  defstruct [:a, :b, :c]
end

Mox.defmock(FooMock, for: Foo)

earn both modules an entry in the report, e.g.

Percentage | Module
-----------|--------------------------
     0.00% | Bar
     0.00% | FooMock
-----------|--------------------------
     0.00% | Total

Is the only way to ignore these types of modules from the final output to explicitly list them in the ignore_modules section, e.g.

def project do
[
    # ...
    test_coverage: [ignore_modules: [Bar, FooMock]]
]
end

There are reasons why we cannot currently use excoveralls or other tools for this (even though ExCoveralls doesn’t “mis-diagnose” these particular cases IIRC). Is there some other way to modify our report? Or is this report actually telling us something useful that I have overlooked?

Thanks for any insights!