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A testiere is armor for the head of a horse and testiere is armor for the head of your defun forms.

1 Testiere

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"
  :tests
  (:program some-test-function)
  (= (1 2) 13)        ; (sum-3 1 2) == 13
  (= (1 2 :z 3) 6)    ; (sum-3 1 2 :z 3) == 6
  (:output (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"))
  :end
  (+ 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 (😉) whose "main loop" involves a good sized collection of unit-testable functions.

1.1 Test Specification

There are a few kinds of tests available.

1.1.1 For 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."
  :tests
  (:program test-fibble)
  :end
  (+ 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.

1.1.2 Basic 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.

  1. Comparator 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."
      :tests
      (:program test-fibble)
      (= (0 0 :z 30) 30)     ; (assert (= (fibble 0 0 :z 30) 30))
      :end
      (+ x y z))
    
    
  2. Other 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 named FUNCTION-NAME with arguments ARGS. This function is meant to act as a test suite for the function being defined with defun/t. It may call that function and ASSERT things about it.
    • (:outputp (..ARGS...) PREDICATE) asserts that the output passes the one-argument predicate.
    • (:afterp (...ARGS...) THUNK) asserts that the thunk should return non-nil after the function has run. Good for testing values of dynamic variables that the function might interact with.
    • (:fails (...ARGS...)) asserts that the function will produce an error with the given arguments.
    • (:signals (...ARGS...) CONDITION) where CONDITION is the name of a condition. Asserts that the function will signal a condition of the supplied type when called with the provided arguments.

1.1.3 Mocking 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

(:let LET-BINDINGS TESTS) 

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

For example

(defvar *count*)

(defun/t increment-count ()
  "Increments the *count* variable."
  :tests
  (: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
  :end
  (incf *count*))

The :with-stubs form is similar, except that it binds temporary values to functions that might be called by the form in questions. Useful for mocking.


(defun just-a-function ()
  (print "Just a function."))

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

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

Created: 2022-11-26 Sat 13:30

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