Interactive Testing for DEFUN

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Colin Okay <colin@cicadas.surf>


A testiere is armor for the head of a horse and testiere is armor

for the head of your defun forms.


With testiere you can program in an interactive TDD-like fashion. Tests are included at the top of a defun/t form. When you recompile your functions interactively, the tests are run. If any fail, you are dropped into a debugger where you can decide to revert the definition to the last known working version, or you can choose to unbind it altogether.

The system supports mocking and stubbing in your tests, so that you can, e.g. test the system in different dynamic contexts or by mocking network request functions.

Here is an example:

(defun/t sum-3 (x y &key (z 10))
  "Sums three numbers, Z has a default value of 10"
  (:program some-test-function)
  (= (1 2) 13)        ; (sum-3 1 2) == 13
  (= (1 2 :z 3) 6)    ; (sum-3 1 2 :z 3) == 6
  (:outputp (0 0)      ; tests that (sum-3 0 0) passes the predicate
           (lambda (result) (= 10 result)))
  (:fails             ; ensures that (sum-3 "strings" "ain't" :z "numbers") fails
   ("strings" "ain't" :z "numbers"))
  (+ x y z))

In the above, a function sum-3 is defined with five embedded tests. The test specification syntax is detailed below. If any of the tests fail, the function will not be redefined and you will drop into the debugger, which asks you how you'd like to proceed.

The approach to TDD-like development taking by testiere may not be appropriate to all circumstances, but it is good for interactive development of interactive applications (ὠ9) whose "main loop" involves a good sized collection of unit-testable functions.

1.1Test Specification

There are a few kinds of tests available.

1.1.1For the Impatient, Just Use :program Tests

Most users will probably benefit from the :program style test. Here is a quick example:

(defun test-fibble ()
  (assert (= 13 (fibble 1 2))))

(defun/t fibble (x y &key (z 10))
  "Adds three numbers, one of which defaults to 10."
  (:program test-fibble)
  (+ x y z))

In the above test, we insist that the test-fibble function not signal an error condition in order for fibble to be successfully (re)compiled.

1.1.2Basic Test Specifications

A test suite is a list of forms that appear between :tests and :end in the body of a defun/t form. The test suite must appear after any optional docstring and before the function body actually begins.

A catalog of test form specifications follows. Test Specifications

(comparator (&rest args...) value)

The comparator should be the name of a binary predicate (like < or eql). These tests proceed by calling (comparator (apply my-fun args) value) If the comparison fails, an error condition is signaled.

Amending the above example, we include a comparator test:

(defun/t fibble (x y &key (z 10))
  "Adds three numbers, one of which defaults to 10."
  (:program test-fibble)
  (= (0 0 :z 30) 30)     ; (assert (= (fibble 0 0 :z 30) 30))
  (+ x y z)) Test Specifications

Every other form appearing in a test suite is a list that starts with a keyword.

  • (:program FUNCTION-NAME ARGS...) runs a function namedFUNCTION-NAME with arguments ARGS. This function is meant to act asa test suite for the function being defined with defun/t. It maycall that function and ASSERT things about it.
  • (:outputp (..ARGS...) PREDICATE) asserts that the output passesthe one-argument predicate.
  • (:afterp (...ARGS...) THUNK) asserts that the thunk should returnnon-nil after the function has run. Good for testing values ofdynamic variables that the function might interact with.
  • (:fails (...ARGS...)) asserts that the function will produce anerror with the given arguments.
  • (:signals (...ARGS...) CONDITION) where CONDITION is the name ofa condition. Asserts that the function will signal a condition ofthe supplied type when called with the provided arguments.

1.1.3Mocking and Stubbing

The following test forms allow for the running of tests inside a context in which certain functions or global values are bound:

Binding variables looks like

and are useful for binding dynamic variables for use during a set oftests.

For example

    (defvar *count*)
    (defun/t increment-count ()
      "Increments the *count* variable."
      (:let ((*count* 4))
        (:afterp () (lambda () (= *count* 5))) ; 5 after the first call
        (= () 6)                               ; 6 after the second
        (:outputp () (lambda (x) (= x 7))))    ; and 7 after the third
      (incf *count*))
The :with-stubs form is similar, except that it binds temporaryvalues to functions that might be called by the form inquestions. Useful for mocking.

    (defun just-a-function ()
      (print "Just a function."))
    (defun/t call-just-a-function ()
      "Calls JUST-A-FUNCTION."
      (:with-stubs ((just-a-function () (print "TEMP JUST-A-FUNCTION.")))
        (equal () "TEMP JUST-A-FUNCTION."))

In the above, the temporary redefinition of JUST-A-FUNCTION is used.

Dependencies (1)

  • trivia

Dependents (1)

  • GitHub
  • Quicklisp