Tuesday, November 01, 2011

Clojure: Non-equality expectations

Clojure Unit Testing with Expectations Part One
Clojure Unit Testing with Expectations Part Two (this entry)
Clojure Unit Testing with Expectations Part Three
Clojure Unit Testing with Expectations Part Four
Clojure Unit Testing with Expectations Part Five
Clojure Unit Testing with Expectations Part Six

In my last blog post I gave examples of how to use expectations to test for equality. This entry will focus on non-equality expectations that are also available.

Regex
expectations allows you to specify that you expect a regex, and if the string matches that regex the expectation passes. The following example shows both the successful and failing expectations that use regexes.

(expect #"in 14" "in 1400 and 92")

jfields$ lein expectations
Ran 1 tests containing 1 assertions in 4 msecs
0 failures, 0 errors.

(expect #"in 14" "in 1300 and 92")

jfields$ lein expectations
failure in (core.clj:17) : sample.test.core
(expect in 14 in 1300 and 92)
regex #"in 14" not found in "in 1300 and 92"
Ran 1 tests containing 1 assertions in 5 msecs
1 failures, 0 errors.
As you can see from the previous example, writing an expectation using a regex is syntactically the same as writing an equality expectation - and this is true for all of the non-equality expectations. In expectations there is only one syntax for expect - it's always (expect expected actual).

Testing for a certain type
I basically never write tests that verify the result of a function is a certain type. However, for the once in a blue moon case where that's what I need, expectations allows me to verify that the result of a function call is a certain type simply by using that type as the expected value. The example below shows the successful and failing examples of testing that the actual is an instance of the expected type.
(expect String "in 1300 and 92")

jfields$ lein expectations
Ran 1 tests containing 1 assertions in 6 msecs
0 failures, 0 errors.

(expect Integer "in 1300 and 92")

jfields$ lein expectations
failure in (core.clj:17) : sample.test.core
(expect Integer in 1300 and 92)
in 1300 and 92 is not an instance of class java.lang.Integer
Ran 1 tests containing 1 assertions in 5 msecs
1 failures, 0 errors.
Expected Exceptions
Expected exceptions are another test that I rarely write; however, when I find myself in need - expectations has me covered.
(expect ArithmeticException (/ 12 0))

jfields$ lein expectations
Ran 1 tests containing 1 assertions in 6 msecs
0 failures, 0 errors.

(expect ClassCastException (/12 0))

jfields$ lein expectations
failure in (core.clj:19) : sample.test.core
(expect ClassCastException (/ 12 0))
(/ 12 0) did not throw ClassCastException
Ran 1 tests containing 1 assertions in 4 msecs
1 failures, 0 errors.
There's another non-equality expectation that I do use fairly often - an expectation where the 'expected' value is a function. The following simple examples demonstrate that if you pass a function as the first argument to expect it will be called with the 'actual' value and it will pass or fail based on what the function returns. (truthy results pass, falsey results fail).
(expect nil? nil)
(expect true? true)
(expect false? true)

jfields$ lein expectations
failure in (core.clj:19) : sample.test.core
(expect false? true)
true is not false?
Ran 3 tests containing 3 assertions in 4 msecs
1 failures, 0 errors.
These are the majority of the non-equality expectations; however, there is one remaining non-equality expectation - in. Using 'in' is fairly straightforward, but since it has examples for vectors, sets, and maps I felt it deserved it's own blog post - coming soon.
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