[plt-scheme] Setup and teardown in SchemeUnit

2008/11/30 Noel Welsh <noelwelsh at gmail.com>:
> I'm heading to sleep, so quickly:
>
> Either:
>
> (check-equal? (before (display "before\n") 0) 0)
>
> Or make the abstraction:
>
> (define (printing-check-equal? v1 v2)
>  (before (display "before\n")
>              (check-equal? v1 v2)))
>
> I'm a bit surprised you want before/after when using checks.  I
> thought they'd only be useful when using test-begin/test-case.

No, you misunderstood me. Sample code was really only a sample code.
:-) I *do* want to use them with test-case.

I want this because I have a piece of setup code that needs to be run
for some subset of tests. Each test needs a clean state, so "before"
macro doesn't work for me here. To draw an example from a different
language, a Python test runner seeing this class:

class TestSuite:
    def setup(self):
        # ...
    def teardown(self):
        # ...
    def test_something(self):
        # ...
    def test_something_else(self):
        # ...

would run tests like that:

  setup()
  test_something()
  teardown()
  setup()
  test_something_else()
  teardown()

As you see, setup & teardown pairs are executed before & after each
test, setting up a well-defined context (a fresh fixture) for each
test case. This is a fairly common testing pattern and probably a main
reason to put test cases into test suites.

"before" and "after" macros in SchemeUnit run given code only once, so
they are no good in this context.

Cheers,
mk