#2986 Add autojunk parameter to SequenceMatcher to optionally disable 'popular == junk' heuristic.
diff --git a/Lib/test/test_difflib.py b/Lib/test/test_difflib.py
index 1b828bb..3533451 100644
--- a/Lib/test/test_difflib.py
+++ b/Lib/test/test_difflib.py
@@ -4,8 +4,47 @@
import doctest
import sys
-class TestSFbugs(unittest.TestCase):
+class TestWithAscii(unittest.TestCase):
+ def test_one_insert(self):
+ sm = difflib.SequenceMatcher(None, 'b' * 100, 'a' + 'b' * 100)
+ self.assertAlmostEqual(sm.ratio(), 0.995, places=3)
+ self.assertEqual(list(sm.get_opcodes()),
+ [ ('insert', 0, 0, 0, 1),
+ ('equal', 0, 100, 1, 101)])
+ sm = difflib.SequenceMatcher(None, 'b' * 100, 'b' * 50 + 'a' + 'b' * 50)
+ self.assertAlmostEqual(sm.ratio(), 0.995, places=3)
+ self.assertEqual(list(sm.get_opcodes()),
+ [ ('equal', 0, 50, 0, 50),
+ ('insert', 50, 50, 50, 51),
+ ('equal', 50, 100, 51, 101)])
+
+ def test_one_delete(self):
+ sm = difflib.SequenceMatcher(None, 'a' * 40 + 'c' + 'b' * 40, 'a' * 40 + 'b' * 40)
+ self.assertAlmostEqual(sm.ratio(), 0.994, places=3)
+ self.assertEqual(list(sm.get_opcodes()),
+ [ ('equal', 0, 40, 0, 40),
+ ('delete', 40, 41, 40, 40),
+ ('equal', 41, 81, 40, 80)])
+
+
+class TestAutojunk(unittest.TestCase):
+ """Tests for the autojunk parameter added in 2.7"""
+ def test_one_insert_homogenous_sequence(self):
+ # By default autojunk=True and the heuristic kicks in for a sequence
+ # of length 200+
+ seq1 = 'b' * 200
+ seq2 = 'a' + 'b' * 200
+
+ sm = difflib.SequenceMatcher(None, seq1, seq2)
+ self.assertAlmostEqual(sm.ratio(), 0, places=3)
+
+ # Now turn the heuristic off
+ sm = difflib.SequenceMatcher(None, seq1, seq2, autojunk=False)
+ self.assertAlmostEqual(sm.ratio(), 0.9975, places=3)
+
+
+class TestSFbugs(unittest.TestCase):
def test_ratio_for_null_seqn(self):
# Check clearing of SF bug 763023
s = difflib.SequenceMatcher(None, [], [])
@@ -184,7 +223,9 @@
def test_main():
difflib.HtmlDiff._default_prefix = 0
Doctests = doctest.DocTestSuite(difflib)
- run_unittest(TestSFpatches, TestSFbugs, TestOutputFormat, Doctests)
+ run_unittest(
+ TestWithAscii, TestAutojunk, TestSFpatches, TestSFbugs,
+ TestOutputFormat, Doctests)
if __name__ == '__main__':
test_main()