add test coverage workflow

[danieleades]

adds a test coverage workflow

job result here - https://app.codecov.io/github/capnproto/capnproto-rust/tree/ci-coverage

[codecov-commenter]

Welcome to Codecov 🎉

Once merged to your default branch, Codecov will compare your coverage reports and display the results in this comment.

Thanks for integrating Codecov - We've got you covered ☂️

[dwrensha]

Cool!

[dwrensha]

Do the tests in capnpc/test/test.rs count towards the coverage of capnpc/? I pushed a95d3e3 and I expected it to increase the reported coverage of target_size(), but it seems that it did not: https://app.codecov.io/github/capnproto/capnproto-rust/commit/a95d3e3adc41dd83b4575512f795430049ed6b27/blob/capnp/src/private/layout.rs#L748

[danieleades]

Do the tests in capnpc/test/test.rs count towards the coverage of capnpc/? I pushed a95d3e3 and I expected it to increase the reported coverage of target_size(), but it seems that it did not: https://app.codecov.io/github/capnproto/capnproto-rust/commit/a95d3e3adc41dd83b4575512f795430049ed6b27/blob/capnp/src/private/layout.rs#L748

the coverage should be counted so long as the following command runs those tests-

          for features in \
            "--no-default-features" \
            "--features sync_reader" \
            "--features unaligned"
          do
            cargo llvm-cov --no-report --doctests --workspace $features

or equivalently if this command runs those tests-

          for features in \
            "--no-default-features" \
            "--features sync_reader" \
            "--features unaligned"
          do
            cargo test --doctests --workspace $features

does that command run the tests you're talking about?

[dwrensha]

Aha, the coverage looks like I expect it to after d27e043:
https://app.codecov.io/github/capnproto/capnproto-rust/commit/d27e043fb0128b4e0eff6292a73e365dd05c9b17/blob/capnp/src/private/layout.rs#L748