Support predicate checks within a collection with =?

[tsmacdonald]

(deftest foo-test
  (is (=? even? 4)) ; passes
  (is (=? {:foo even?} {:foo 42})) ; passes
  (is (=? #{even?} #{2 4 6 8})))  ; fails: expected #{even?}, actual #{2 4 6 8}

If there's a collection that includes exactly one item which is a predicate function, I think =? should check that the actual value is of the given collection type and all of its elements pass the predicate.

Motivating example in the wild from Metabase

[crisptrutski]

The support I wanted was not for broadcasting a single predicate, but to support matching between sets of equal size. In general this is a bipartite mapping problem that can't be solved greedily, but a greedy approach is probably good enough for 99.9% of cases.

Another tricky things is disambiguating sets as collections or functions.

What I want:

(is (=? #{#{1} even? zero?} #{0 2 1})) ;; true
(is (=? #{#{1} even? zero?} #{2 1})) ;; false
(is (=? #{#{1} even? zero?} #{2 1 4 0})) ;; false