(deftest arithmetic-works  (testing "with positive integers"    (is (= (+ 2 2) 4))    (is (= (+ 3 4) 7)))

 (facts "on arithmetic"  (fact "you can sum positive integers"    (+ 2 2) => 4    (+ 1000 1000 1000 1000)    => 4000))

 (fact (+ 3 4) => prime?)

 (facts  (empty? []) => truthy  (empty? [3]) => falsey)

 (fact "the universe won't divide"
      (/ 1 0) => (throws Exception))

 (fact
   (range 10) => (contains 5) ;; [0, 1, 2, 3, ..., 9]
   (range  3) => (just [even? odd? even?]))

 (fact
   {:age 27 :laughter "huahue"} => (contains {:age #(>= % 18)})
   {:age 27 :laughter "huahue"} => (just {:age #(>= % 18) 
                                          :laughter #"(hu[a|e])+"}))

 (fact 
   #{:foo :bar} => (contains :foo)
   #{:foo :bar} => (two-of keyword?))

 (fact   (room-temperature) => (roughly 25 3)   (provided     (object-temperature) =streams=> [85 86 87]))

 (fact  (gen-positive-number) =not=> #(< % 0))

 (defn burger-combo [burger]    {:burger burger :free-drink (cheapest-drink)})

 (fact "you get a free drink with the combo"   (burger-combo "delicious burger")   =contains=> {:free-drink "delicious drink"}   (provided (cheapest-drink) => "delicious drink"))

 (fact "you get a free drink with the combo"   (burger-combo ..some-burger..)    =contains=> {:free-drink ..some-drink..}  (provided (cheapest-drink) => ..some-drink..))

 (fact "the charge with the highest value is charged in the end"  (divide-charges 9) => [4 5]) 

 (tabular (fact "..."            (divide-charges ?total) => [?1st ?2nd])           ?total    ?1st    ?2nd           100       50      50           99        49      50)