ANTLR Python Lexer unit-testing

antlr_lexer_test.py

from antlr4 import CommonTokenStream, InputStream, Token
# from mytool.parsers.error_listener import MyErrorListener


def getTokensFromText(input_string, MyLexer):
    input_stream = InputStream(input_string)
    lexer = MyLexer(input_stream)
    # lexer.addErrorListener(MyErrorListener)
    stream = CommonTokenStream(lexer)
    stream.fill()
    return stream.tokens

def test_lexer_bad_input(self):
    from mytool.parsers.Lexer import Lexer as MyToolsLexer
    tokens = getTokensFromText("function ()", MyToolsLexer)  # assumes MyLexer won't detect/parse "function ()"
    self.assertEqual(1, len(tokens)) #// includes EOF
    self.assertEqual(Token.EOF, tokens[0].type)