How to avoid returning 'nil' after string in Clojure?

Question

I'm working on an exercise in Clojure (answering input based on if it's a question, written in capital letters and so on) and while it works, I can't pass the required test because my code returns nil along with every correct answer. How can I avoid that?

(ns bob
  (:use [clojure.string :only [upper-case blank?]]))

(defn- silence? [question]
  (blank? question))

(defn- yell? [question]
  (and (re-find #".*!$" question) (= question (upper-case question))))

(defn- ask? [question]
  (re-find #".*\?$" question))

(defn response-for [question]
  (if (silence? "Fine, be that way.")
    (case ((juxt yell? ask?) question)
      [true true] "Calm down, I know what I'm doing!"
      [true false] "Woah, chill out!"
      [false true] "Sure."
      "Whatever.")))

Example from the test:

FAIL in (responds-to-forceful-talking) (bob_test.clj:25)
expected: (= "Whatever." (bob/response-for "Let's go make out behind the gym!"))
  actual: (not (= "Whatever." nil))

Thank you in advance!

Answer 1

As John commented your issue is in if, follows some adjustments to fix it:

(defn response-for [question]
  (if (silence? question)
    "Fine, be that way."
    (case ((juxt yell? ask?) question)
      [true true] "Calm down, I know what I'm doing!"
      [true false] "Woah, chill out!"
      [false true] "Sure."
      "Whatever.")))
      
(= "Whatever." (bob/response-for "Let's go make out behind the gym!"))