Testing map with timestamp value in Clojure

I am testing a function in Clojure which takes a map as input and outputs a map to which the field :timestamp (current-timestamp) is added.

I have problems testing for equality as I cannot predict which timestamp will be added by the function.

(is (= output (convert-map input)))

I thought about dissoc-ing the :timestamp from the output of the function but that seems convoluted, so I wonder if there is a better solution.