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doc-test is a Clojure namespace that provides Python-like doctests [1].
Examples are very useful in documentation and help to clarify the
meaning of descriptions. Take #'clojure.set/join:
"When passed 2 rels, returns the rel corresponding to the natural
join. When passed an additional keymap, joins on the corresponding
Que? A simple example is much more clear for someone reading the docs
for the first time:
(def languages
#{{:name "C" :type "procedural"}
{:name "Clojure" :type "functional"}
{:name "Haskell" :type "functional"}})
(def fun-level
#{{:type "procedural" :funness "meh"}
{:type "functional" :funness "awesome"}})
=> (clojure.set/join languages fun-level)
#{{:name "Haskell", :type "functional", :funness "awesome"}
{:name "Clojure", :type "functional", :funness "awesome"}
{:name "C", :type "procedural", :funness "meh"}}
Awesome. The only problem is that sometimes documentation and actual
code fall out of sync with each other. Doc-tests provide a way to
assure that doesn't happen. The examples in the documentation are
tested with the rest of the code!
Here's an example function with some doc-tests:
(defn adder
"A simple function to test the doctest macro with.
=> ((adder 1) 2)
4 ; incorrect!
=> ((adder 4) 5)
(fn [n2] (+ n1 n2)))
To generate the tests from #'adder's doc-string:
(doc-test adder)
Put this wherever you've put the rest of your
#'clojure.test/deftests. When the above test is run this error occurs:
FAIL in (adder__doc-test__88) (doc_test_tests.clj:19)
expected: (clojure.core/= ((adder 1) 2) (quote 4))
actual: (not (clojure.core/= 3 4))
Doc-test makes efforts to make test failures easier to debug. Because
your documentation is turned into standard clojure.test declarations,
we see the failure display in the same way. The test name is the
symbol's name along with "__doc-test__". The expected and actual
statements are also exactly what was in the doc-string.