Expects the expression to thrown an exception.

If the expression does throw, then the exception is caught, bound to the symbol, and the body is evaluated.

The body can then perform tests on the details of the exceptions.

Otherwise, if no exception is thrown, then a new exception is thrown, detailing the expression that was expected to fail.

sym

symbol that we be bound to the exception thrown from the expression

exp

expression to evaluate

body

evaluated with sym bound

Example:

(is-thrown [e (parse-invalid-file "invalid.txt")]
  (is (= :parse/failure
      (-> e ex-data :type))))

Evaulates to nil.