trying to do this:

(fact "contains should work when nesting"
      (-> ..col.. (get 0) :k) => ..v..
      (provided
        ..col.. =contains=> [..m..]
        ..m.. =contains=> {:k ..v..}))

"contains should work when nesting" at (bla.clj:2)
    Expected: ..v..
      Actual: nil

is that the expected behavior?

^ right

actual => expected

the Actual is the value returned by the function you used, the Expected is the value you specified

hm, not sure if I understood, but this is valid code:

(fact (:k ..m..) => ..v..
         (provided ..m.. =contains=> {:k ..v..}))

the problem is that it doesn't work when you nest a metaconstant inside another with =contains=>

https://github.com/marick/Midje/wiki/Data-Prerequisites