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    Simple trick for testing forms full of checkboxes with django

    In late 2011 I hope we can all agree that unit testing is pretty important when creating websites or almost anything. Doesn't really matter whether you prefer a blackbox integration testing approach or a strict unit testing style. What matters is that you have tests.

    English: A series of build lights.

    But what do you do when you want to test a form with a bunch of checkboxes?

    You want to make sure all combinations of on/off tests are working. But with even just 6 checkboxes that's 2^6=64 test and ... well nobody in their right mind is going to write that many tests are they?

    Last weekend I came up with a simple solution to this problem, dare I say elegant.

    The approach is to make a list of checkboxes, then generate binary numbers from 0 to 2^(length of list). Then simply iterate over the generated binary numbers, pick all the checkboxes with a corresponding true bit in the number and run its test - the tests are lambda functions in a dictionary.

    My code was complicated slightly because I had two distinct sets of checkboxes that had to be tested separately-ish, but here's what this basically looks like in code.

    _columns = ['job_code', 'location_in', 'location_out', 'shift_report']
    def checkboxes(self):
    checks = []
    for i in range(2**len(self._columns):
    column_switch = bin(j)[2:].rjust(4, '0')
    checks.append([name for (yes, name) in
    zip(column_switch, self._columns) if int(yes)])
    return checks

    You also need to define the actual tests for all the checkboxes, deciding how thorough to be is a matter of personal taste, I like to test for the smallest possible symptom.

    _column_checks = {
    'job_code': {True: lambda r:
    self.assert_('Job Code' in r.content,
    "no code column"),
    False: lambda r:
    self.assert_('Job Code' not in r.content,
    "is code column")},
    # and so on (this example has been violently snipped, likely missing a } or two

    ' in r.content, "no code column"), False: lambda r: self.assert_('Job Code

    ' not in r.content, "is code column")}, # and so on

    And finally the whole thing becomes a simple loop

    for checkboxes in self.checkboxes():
    # do a bunch of posts to django to set everything up
    for check in _column_checks.keys():
    _column_checks[check][check in checkboxes['columns']](response)

    And that's it. Simple easily modifiable code to test every possible combination of all checkboxes in a form.

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    Published on December 2nd, 2011 in Checkbox, django, Programming, python, Software testing, Tick (check mark), Uncategorized, Unit testing

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