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53 lines
1.9 KiB
Python
53 lines
1.9 KiB
Python
#
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# This file is for everybody to add tests for bugs that aren't
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# fixed yet. Please add a test case and appropriate bug description.
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#
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# When you fix one of the bugs, please move the test to the correct
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# test_ module.
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#
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import unittest
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from test import test_support
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#
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# One test case for outstanding bugs at the moment:
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#
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class TestDifflibLongestMatch(unittest.TestCase):
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# From Patch #1678339:
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# The find_longest_match method in the difflib's SequenceMatcher has a bug.
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# The bug is in turn caused by a problem with creating a b2j mapping which
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# should contain a list of indices for each of the list elements in b.
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# However, when the b2j mapping is being created (this is being done in
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# __chain_b method in the SequenceMatcher) the mapping becomes broken. The
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# cause of this is that for the frequently used elements the list of indices
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# is removed and the element is being enlisted in the populardict mapping.
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# The test case tries to match two strings like:
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# abbbbbb.... and ...bbbbbbc
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# The number of b is equal and the find_longest_match should have returned
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# the proper amount. However, in case the number of "b"s is large enough, the
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# method reports that the length of the longest common substring is 0. It
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# simply can't find it.
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# A bug was raised some time ago on this matter. It's ID is 1528074.
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def test_find_longest_match(self):
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import difflib
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for i in (190, 200, 210):
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text1 = "a" + "b"*i
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text2 = "b"*i + "c"
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m = difflib.SequenceMatcher(None, text1, text2)
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(aptr, bptr, l) = m.find_longest_match(0, len(text1), 0, len(text2))
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self.assertEquals(i, l)
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self.assertEquals(aptr, 1)
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self.assertEquals(bptr, 0)
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def test_main():
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test_support.run_unittest(TestDifflibLongestMatch)
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if __name__ == "__main__":
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test_main()
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