Multiple-answer problems need assert!(matches!(expr, pat | pat)

[workingjubilee]

I rewrote some test code here to use patterns in the asserts so that it is correct even if the sort ordering generated by sort_unstable_by changes.

[workingjubilee]

Without this your code fails on the nightly version because it depends on unspecified implementation details of the standard library which are deliberately subject to change without notice, because we would like to continue improving its internals.

failures:

---- sort_characters_by_frequency::tests::test stdout ----
thread 'sort_characters_by_frequency::tests::test' panicked at leetcode/src/00451_sort_characters_by_frequency/solution.rs:27:9:
assertion `left == right` failed
  left: "eetr"
 right: "eert"
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    sort_characters_by_frequency::tests::test

test result: FAILED. 396 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.11s

[lht102]

I missed the PR and just get back to this repo recently. sorry for the late reply.
thanks for that!

I found this is amazing that rust team had built something to find regression after updating the sort implementation. this is very cool.