Clojure "is" assertion not working as expected

Question

I am writing test cases for my first Clojure project. Here, I want the test to fail if the value of ":meat" is empty :

(deftest order-sandwich
  (let [response {:meat "" :bread "yes" :add-on "lettuce"}]
    (is (= (:bread response) "yes"))
    (is (not (nil? (:meat response))))))

But my test runs successfully (returning "nil") .

Anybody know why this happens? Is there a better way to do this?

I thank you in advance!!

Thank you @AlanThompson for the edit.! – Snehaa Ganesan Mar 15 '19 at 16:25 — Snehaa Ganesan, Mar 15 '19 at 16:25

Carcigenicate · Accepted Answer · 2019-03-16T13:50:30.457

6

An empty String is not nil:

(nil? "")
=> false

You want to test if it's empty, not nil, which can be done using seq or empty? (among other ways):

(is (not (empty? (:meat response))))
; Or use not-empty

; There's also the arguably more idiomatic way

(is (seq (:meat response)))

edited Mar 16 '19 at 13:50

answered Mar 14 '19 at 21:00

Carcigenicate

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Thank you @Carcigenicate for the input, that works! – Snehaa Ganesan Mar 14 '19 at 21:03
@SnehaaGanesan No problem. Glad to help. – Carcigenicate Mar 14 '19 at 21:05
(is (= false (empty? (:meat response)))) works too !! – Snehaa Ganesan Mar 14 '19 at 21:07
4

@SnehaaGanesan Yes. It's often not advisable to check against `true`/`false` though. That would be like in Java doing something like `if(someVar == true)`. It's redundant. You might as well just write `if(someVar)`, or `if(!someVar)` if you need it negated. – Carcigenicate Mar 14 '19 at 21:09
1

@SnehaaGanesan also relevant: like the empty string zero is truthy in clojure which can throw people coming from various languages where that's not the case. – Jared Smith Mar 15 '19 at 13:36
@Carcigenicate I see, thank you for the explanation!! – Snehaa Ganesan Mar 15 '19 at 16:04
You may also use `not-empty`: `(is (not-empty (:meat response)))` – Juraj Martinka Mar 16 '19 at 10:43
@JurajMartinka Added. – Carcigenicate Mar 16 '19 at 13:50

Clojure "is" assertion not working as expected

1 Answers1