如何编写测试来处理预期的异常？

Question

如何测试抛出预期异常的函数？这是抛出异常的函数:

(defn seq-of-maps?
  "Tests for a sequence of maps, and throws a custom exception if not."
  [s-o-m]
  (if-not (seq? s-o-m)
    (throw (IllegalArgumentException. "s-o-m is not a sequence"))
    (if-not (map? (first s-o-m))
      (throw (IllegalArgumentException. "s-o-m is not a sequence of maps."))
      true)))

我想设计一个如下所示的测试,其中抛出异常并捕获然后进行比较.以下不起作用:

(deftest test-seq-of-maps
  (let [map1  {:key1 "val1"}
        empv  []
        s-o-m (list {:key1 "val1"}{:key2 "val2"})
        excp1 (try 
                (seq-of-maps? map1)
                (catch Exception e (.getMessage e)))]
    (is (seq-of-maps? s-o-m))
    (is (not (= excp1 "s-o-m is not a sequence")))))

我收到这些错误:

Testing util.test.core

FAIL in (test-seq-of-maps) (core.clj:27)
expected: (not (= excp1 "s-o-m is not a sequence"))
  actual: (not (not true))

Ran 2 tests containing 6 assertions.
1 failures, 0 errors.    

显然,我缺少一些关于编写测试的东西.我很难搞清楚这一点.我的项目是用lein new建立的,我用lein测试运行测试.

谢谢.

Answer 1

测试中的最后一个断言是不正确的; 它应该是(is (= excp1 "s-o-m is not a sequence"))因为map1不是map的seq.

除此之外,使用(is (thrown? ..))或(is (thrown-with-msg? ...))检查抛出的异常可能更清楚.