def test(grammarText, sentences):
"""Test the coverage of a CFG grammar.
grammarText -- the grammar string
sentences -- a list of sentences to test, with invalid ones prefixed with '*'
"""
valid_sentences = [s for s in sentences if s[0] != '*']
invalid_sentences = [s[1:] for s in sentences if s[0] == '*']
parser = ChartParser(parse_cfg(grammarText))
for sentence in valid_sentences:
parses = parser.nbest_parse(sentence.split())
print(sentence + "\n" + "\n".join(map(str, parses)) + "\n")
assert parses, "Valid sentence failed to parse."
for sentence in invalid_sentences:
print("*" + sentence)
parses = parser.nbest_parse(sentence.split())
assert parses == [], "Invalid sentence parsed successfully."
