A new syntax for writing tests

jfine jonathan.fine1 at googlemail.com
Thu Aug 5 15:07:32 CEST 2010


On 5 Aug, 10:17, Jean-Michel Pichavant <jeanmic... at sequans.com> wrote:
> Jonathan Fine wrote:
> > Hi
>
> > I just discovered today anewsyntaxfor writing tests.  The basic
> > idea is to write a function that contains some statements, and run it
> > via a decorator.  I wonder if anyone had seen this pattern before, and
> > how you feel about it.  For myself, I quite like it.
>
> > Let's suppose we want to test this trivial (of course) class.
> >     class Adder(object):
>
> >         def __init__(self):
> >             self.value = 0
>
> >         def plus(self, delta):
> >             self.value += delta
>
> > The test the class you need a runner.  In this case it is quite simple.
>
> >     def runner(script, expect):
> >         '''Create an adder, run script, expect value.'''
>
> >         adder = Adder()
> >         script(adder)
> >         return adder.value
>
> > We can now create (and run if we wish) a test.  To do this we write
>
> >     @testit(runner, 4)
> >     def whatever(a):
> >         '''Two plus two is four.'''
>
> >         a.plus(2)
> >         a.plus(2)
>
> > Depending on the exact value of the testit decorator (which in the end
> > is up to you) we can store the test, or execute it immediately, or do
> > something else.
>
> > The simplest implementation prints:
> >     OK: Two plus two is four.
> > for this passing test, and
> >     Fail: Two plus four is five.
> >       expect 5
> >       actual 6
> > for a test that fails.
>
> > Here is the testit decorator used to produce the above output:
>
> >     def testit(runner, expect):
> >         '''Test statements decorator.'''
>
> >         def next(script):
> >             actual = runner(script, expect)
> >             if actual == expect:
> >                 print 'OK:', script.__doc__
> >             else:
> >                 print 'Fail:', script.__doc__
> >                 print '  expect', expect
> >                 print '  actual', actual
>
> >         return next
>
> > You can pick this code, for at least the next 30 days, at
> >    http://dpaste.com/hold/225056/
>
> > For me the key benefit is that writing the test is really easy.  
> > Here's a test I wrote earlier today.
>
> > @testit(runner, '''<a att="value"><b/></a>''')
> > def whatever(tb):
> >     tb.start('a', {'att': 'value'})
> >     tb.start('b')
> >     tb.end('b')
> >     tb.end('a')
>
> > If the test has a set-up and tear-down, this can be handled in the
> > runner, as can the test script raising an expected or unexpected
> > exception.
>
> Hi,
>
> "The unittest module provides a rich set of tools for constructing and
> running tests. This section demonstrates that a small subset of the
> tools suffice to meet the needs of most users."
>
> sourcehttp://docs.python.org/library/unittest.html
>
> As you can see, a much more featured test framework already exists.
>
> There's nothing wrong in anewtest framework, but it has to be better
> than the existing one in some situations.

Chalk and cheese.

My concern is to make tests easy to write, and that is something that
unittest is, in my view, not good at.  It is, as you say, a *test
framework*.

I've not written a test framework.  I've found what seems to be a new
*syntax* for writing tests.  Tests written in the new syntax can be
run in the unittest (or any other) framework.

--
Jonathan




More information about the Python-list mailing list