[EnesKartal]

Fixes #535

Checklist

• My branch is up-to-date with main branch.
• Everything works and tested on latest stable Rust.
• Coverage and Linting have been applied

Current behaviour

src/metrics/tests_edge_cases.rs is not declared in src/metrics/mod.rs, so its 26 tests are never built. If you declare it, it does not compile:

• it imports MeanSquaredError, but the type is MeanSquareError;
• the HCV tests import homogeneity_score, completeness_score and v_measure_score from metrics::cluster_hcv, but these functions are in metrics;
• these three functions require T: Number + FloatNumber + RealNumber + Ord. FloatNumber is only on f32/f64, which are not Ord, so no type can call them.

New expected behaviour

• mod.rs declares #[cfg(test)] mod tests_edge_cases;, and the imports are fixed.
• homogeneity_score, completeness_score and v_measure_score now use T: Number + Ord. This is the bound of ClusterMetrics::hcv_score(), which is the only thing they call. The bounds are less strict than before, so no caller breaks, and the functions now work with integer labels (for example Vec<u32>), as the HCV edge-case tests use them.
• cargo fmt reformatted the test file (it was never checked before, because it was not part of the crate). I also changed four x >= 0.0 && x <= 1.0 asserts to (0.0..=1.0).contains(&x) so that cargo clippy --all-targets has no warnings in the file.

Test plan

# before (main): the edge-case tests are not part of the build
$ cargo test --lib metrics
test result: ok. 54 passed; 0 failed; ...

# before, with only the `mod tests_edge_cases;` line added
error[E0432]: unresolved import `crate::metrics::mean_squared_error::MeanSquaredError`
error[E0432]: unresolved imports `crate::metrics::cluster_hcv::homogeneity_score`, ...

# after
$ cargo test --lib metrics_edge_cases
test result: ok. 26 passed; 0 failed; ...
$ cargo test --lib metrics
test result: ok. 80 passed; 0 failed; ...

cargo fmt --check and cargo clippy --all-features --all-targets -- -Drust-2018-idioms show nothing for the changed files.

Note: the other tests_edge_cases.rs files (cluster, decomposition, ensemble, linear, naive_bayes, neighbors, svm, tree) are also not declared in their mod.rs. I did not change them in this PR, to keep it focused on #535.

Change logs

Changed

• homogeneity_score, completeness_score and v_measure_score accept T: Number + Ord labels.
• The metrics edge-case tests are compiled and run.