how to make all assertions in a unit test execute

Ben Finney ben+python at benfinney.id.au
Sun Oct 17 00:05:39 CEST 2010


jimgardener <jimgardener at gmail.com> writes:

> class FileNamesTest(unittest.TestCase):
>      def setUp(self):
>         self.dirname='/home/me/data'
>
>     def test_get_filenames(self):
>         innerstr='tom'
>         matching_names=get_filenames(self.dirname,innerstr)
>         self.assertEquals(1,len(matching_names))
>
>         innerstr='myself'
>         matching_names=get_filenames(self.dirname,innerstr)
>         self.assertEquals(0,len(matching_names))
>
>         innerstr='jerry'
>         matching_names=get_filenames(self.dirname,innerstr)
>         self.assertEquals(3,len(matching_names))

A side point unrelated to the question: your code will be easier to read
if you follow PEP 8, specifically its recommendations regarding spaces
around syntax (like ‘=’ and ‘,’).

> when I run the unittest, if the test fails at the first assertion,the
> other assertions are not executed at all.

Yes, that's by design. Each function in a TestCase subclass is a test
case; the function goes about testing *one thing*, and ends as soon as
the test passes or fails.

> How do I organize the test so that all assertions can run?

Every test case should test exactly one true-or-false question. Name
each test case after the assertion it's making, so the unittest output
makes sense.

    class get_filenames_TestCase(unittest.TestCase):
         def setUp(self):
            self.dirname = '/home/me/data'

        def test_one_match_returns_one_item(self):
            innerstr = 'tom'
            matching_names = get_filenames(self.dirname, innerstr)
            self.assertEquals(1, len(matching_names))

        def test_no_match_returns_empty_sequence(self):
            innerstr = 'myself'
            matching_names = get_filenames(self.dirname, innerstr)
            self.assertEquals(0, len(matching_names))

        def test_three_matches_returns_three_items(self):
            innerstr = 'jerry'
            matching_names = get_filenames(self.dirname, innerstr)
            self.assertEquals(3, len(matching_names))

Also, be aware that each test case should be independent of the others:
any common set-up should be in a fixture, created in ‘setUp’ and reset
(if necessary) in ‘tearDown’.

-- 
 \           “I do not believe in forgiveness as it is preached by the |
  `\        church. We do not need the forgiveness of God, but of each |
_o__)                    other and of ourselves.” —Robert G. Ingersoll |
Ben Finney



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