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Saturday, November 28, 2009

Namespaces and Unit Tests

OK, if I'm going to be doing this for more than toy programs I need to learn how to use the namespace and unit testing facilities

Here I'm typing at the repl, or more accurately I have this file open in emacs and I'm passing the expressions one by one to the repl.

(ns namespaces-and-tests
  (:use clojure.test))

here's a factorial, with some tests included


    (defn factorial [n]
      (if (< n 3) n
          (* n (factorial (dec n)))))

  (is ( = (factorial 1)     1) "base case")
  (is ( = (factorial 4)     (* 1 2 3 4)) "first recursion")
  (is ( = (factorial 10)    (apply * (range 1 10))) "general case" ))

I can run my tests like so:


or like

(run-tests 'namespaces-and-tests)

I can also define a separate factorial testing function, perhaps even in a different namespace

(ns separate-tests
  (:use clojure.test))

(use 'namespaces-and-tests);;however this breaks, whining something about classpaths and non-existent files
(ns-publics 'namespaces-and-tests) ;;even though we can still see the namespace and its function

(namespaces-and-tests/factorial 4) ;;and indeed it still works!

It appears that require defines libraries by filename, whilst refer talks about namespaces. use is a combination of the two.

(refer 'namespaces-and-tests) ;;try this instead
(factorial 4)      ;;aha!

So here is a more complex test for the factorial

(deftest factorial-tests
  (testing "factorial"
    (testing "base cases"
      (is (= (factorial 1) 1))
      (is (= (factorial 2) 2))
      (is (= (factorial 0) 0)))
    (testing "general case"
      (is ( = (factorial 10) (apply * (range 1 11))))
      (is ( = (factorial 10000) (apply * (range 1 10001))) "tail recursion"))
    (testing "bad arguments"
      (is (thrown? java.lang.StackOverflowError (factorial -1)))
      (is (thrown? java.lang.StackOverflowError (factorial 0.5))))))

which we can run like this:

(run-tests 'separate-tests)

or like this


we can run both at once with

(run-tests 'namespaces-and-tests 'separate-tests)

or we can use


which claims to be testing everything in the clojure libraries, and in swank, which I'm using to connect clojure to emacs, but doesn't actually seem to do any testing on them. Bug perhaps?

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