Exercise 49: Too Good to be True?

Python
#1

I have created my ex49(really ex48) parser_tests.py file and I had a few errors and overall rough time with the first couple of test functions, but after those first 3 test functions, I never encountered an error and all my nosetest functions passed first try. I figured this too good to be true. Would anyone mind looking at my code and provide feedback on where I went wrong, that is if I did, which I highly suspect I did.

My code:

from nose.tools import * # noqa
from ex48 import lexicon, parser


def test_sentence():
    """ test 'sentence' function """
    s1 = parser.Sentence(('noun', "player"),
                         ('verb', "attacks"),
                         ('noun', "rat"))
    assert s1.verb == "attacks"
    assert s1.subject == "player"
    assert s1.object == "rat"


def test_peek():
    """ test 'peek' function """
    word_list = lexicon.scan("princess kill bear")
    assert "noun" == parser.peek(word_list)


def test_match():
    """ test 'match' function """
    word_list = lexicon.scan("bear eat princess")
    assert_equal(('noun', "bear"), parser.match(word_list, 'noun'))
    assert_equal(None, parser.match(word_list, 'noun'))


def test_skip():
    """ test 'skip' function """
    word_list = lexicon.scan("princess kill the bear")
    assert_equal(('noun', "princess"), parser.match(word_list, 'noun'))
    assert_equal(('verb', "kill"), parser.match(word_list, 'verb'))
    assert_equal(('stop', "the"), parser.match(word_list, 'stop'))
    assert_equal(('noun', "bear"), parser.match(word_list, 'noun'))
    assert_equal(None, parser.skip(word_list, 'stop'))


def test_parse_verb():
    """ test 'parse_verb' function """
    word_list = lexicon.scan("princess kill the bear")
    assert_equal(('noun', "princess"), parser.match(word_list, 'noun'))
    assert_equal(parser.parse_verb(word_list), ('verb', "kill"))


def test_parse_object():
    """ test 'parse_object' function """
    word_list = lexicon.scan("princess kill the bear")
    assert_equal(parser.parse_object(word_list), ('noun', "princess"))


def test_parse_subject():
    """ test 'parse_subject' function """
    word_list = lexicon.scan("go north")
    assert_equal(parser.parse_subject(word_list), ('noun', "player"))
    # test again
    word_list = lexicon.scan("princess kill the bear")
    assert_equal(parser.parse_subject(word_list), ('noun', "princess"))


def test_parse_sentence():
    """ test 'parse_sentence' function """
    word_list = lexicon.scan("princess kill the bear")
    s = parser.parse_sentence(word_list)

    assert s.subject == "princess"
    assert s.verb == "kill"
    assert s.object == "bear"

    # test again
    word_list = lexicon.scan("go north")
    s = parser.parse_sentence(word_list)

    assert s.subject == "player"
    assert s.verb == "go"
    assert s.object == "north"

    # test again
    word_list = lexicon.scan("north")
    assert_raises(parser.ParserError, parser.parse_sentence, word_list)

Thank you

#2

What you should do is try to write some tests that you know should fail, just to make sure you are actually testing the code you think you are. If you write a failing test and it does NOT fail, then you know your tests are doing nothing.