memoization tests

tests/unit/regressions/test_memoization.py

+from StringIO import StringIO
+import sys
+from arpeggio import ParserPython
+
+
+def test_memoization_positive(capsys):
+    '''
+    Test that already matched rule is found in the cache on
+    subsequent matches.
+    Args:
+        capsys - pytest fixture for output capture
+    '''
+
+    def grammar():  return [(rule1, ruleb), (rule1, rulec)]
+    def rule1():    return rulea, ruleb
+    def rulea():    return "a"
+    def ruleb():    return "b"
+    def rulec():    return "c"
+
+    parser = ParserPython(grammar, debug=True)
+
+    # Parse input where a rule1 will match but ruleb will fail
+    # Second sequence will try rule1 again on the same location
+    # and result should be found in the cache.
+    parse_tree = parser.parse("a b c")
+
+    # Assert that cached result is used
+    assert  "Cache hit" in capsys.readouterr()[0]
+
+def test_memoization_nomatch(capsys):
+    '''
+    Test that already failed match is found in the cache on
+    subsequent matches.
+    '''
+
+    def grammar():  return [(rule1, ruleb), [rule1, rulec]]
+    def rule1():    return rulea, ruleb
+    def rulea():    return "a"
+    def ruleb():    return "b"
+    def rulec():    return "c"
+
+    parser = ParserPython(grammar, debug=True)
+    parse_tree = parser.parse("c")
+
+    assert  "Cache hit for [rule1(Sequence), 0] = 'Expected 'grammar' at position (1, 1)" in capsys.readouterr()[0]
+
+