Tuesday, November 01, 2011

Clojure: expectations with values in vectors, sets, and maps

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

I've previously written about verifying equality and the various non-equality expectations that are available. This entry will focus on another type of comparison that is allowed in expectations - verifying that an 'expected' value is in an 'actual' value.

A quick recap - expectations generally look like this: (expect expected actual)

verifying an expected value is in an actual value is straightforward and hopefully not a surprising syntax: (expect expected (in actual))

If that's not clear, these examples should make the concept completely clear.
;; expect a k/v pair in a map.
(expect {:foo 1} (in {:foo 1 :cat 4}))

;; expect a key in a set
(expect :foo (in #{:foo :bar}))

;; expect a val in a list
(expect :foo (in [:foo :bar]))
As you would expect, running these expectations results in 3 passing tests.
jfields$ lein expectations
Ran 3 tests containing 3 assertions in 8 msecs
0 failures, 0 errors.
As usual, I'll show the failures as well.
;; expect a k/v pair in a map.
(expect {:foo 2} (in {:foo 1 :cat 4}))

;; expect a key in a set
(expect :baz (in #{:foo :bar}))

;; expect a val in a list
(expect :baz (in [:foo :bar]))

jfields$ lein expectations
failure in (core.clj:18) : sample.test.core
(expect {:foo 2} (in {:foo 1, :cat 4}))
expected: {:foo 2}
in: {:foo 1, :cat 4}
:foo expected: 2
was: 1
failure in (core.clj:21) : sample.test.core
(expect :baz (in #{:foo :bar}))
key :baz not found in #{:foo :bar}
failure in (core.clj:24) : sample.test.core
(expect :baz (in [:foo :bar]))
value :baz not found in [:foo :bar]
expectations does it's best to provide you with any additional info that might be helpful. In the case of the vector and the set there's not much else that can be said; however, the map failure gives you additional information that can be used to track down the issue.

There's nothing magical going on with 'in' expectations and you could easily do the equivalent with select-keys, contains?, or some, but expectations allows you to get that behavior while keeping your tests succinct.
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