See https://internals.rust-lang.org/t/help-us-test-the-breaking-bug-fix-to-cargo-features/7317 and rust-lang/cargo#5364. Also see the current .travis.yml where cargo test is run once for uom and once for feature_check.

Currently if you use cargo --test --all workspace crates are compiled with their default features (--features does not affect them) and link against the root package that is built with the specified features including dev-dependencies. If you use cargo test --manifest-path ... to manually run test for a workspace crate that references the root package then the root package is recompiled without dev-dependencies.

Ideally the uom CI build scripts should run both uom and feature_check tests and only compile uom once.

A possible short term fix is to have feature_check use the same feature set in the cargo build invocation so those build artifacts can be reused.