Midje print stacktrace when test fails

Question

I am learning Clojure, and trying to use TDD to do so *.

I use midje as a testing library. Love it so far, the expected versus actual results display is very helpfull.

But is there was a way to use clojure.tools.trace or something similar to print the trace of the first test that fails ?

_{*: Specifically, I remember seeing a talk by Robert C. Martin about the transformation priority premise, and I'm implementing a factorial function this way. There isn't yet much code to show though.}

Answer 1

One possibility would be writing your own emitter but that might be overkill for your specific goal.

Alternatively, you can monkey-patch the function responsible for formatting the expected values:

(require '[midje.util.exceptions :as e]
         '[midje.emission.plugins.util :as u])

(defn- format-captured-throwable
  [ex]
  (if (e/captured-throwable? ex)
    ;; ... adjust this to your needs ...
    (pr-str 'this-is-your-exception (e/throwable ex))))

(alter-var-root
  #'u/attractively-stringified-value
  (fn [f]
    #(or (format-captured-throwable %) (f %))))

format-captured-throwable has to produce a string, though, meaning that directly printing the stacktrace will let it end up nowhere near midje's test report.

user=> (fact (throw (Exception. "khaaaaaaaan.")) => :not-khan)

FAIL at (form-init4689442922606051135.clj:1)
    Expected: :not-khan
      Actual: this-is-your-exception #<Exception java.lang.Exception: khaaaaaaaan.>