I am learning Python through LPTHW. There is an exercise where we need to create test scenarios. The following is the code for whom Test Case have to be made:

#############################
#   Sentence Parser         #
#############################

class ParserError(Exception):
    pass

class Sentence(Object):

    def __init__(self, subject, verb, object):
        # remember, we take ('noun','princess') and convert them
        self.subject = subject[1]
        self.verb = verb[1]
        self.object = object[1]

def peek(word_list):
    if word_list:
        word = word_list[0]
        return word[0]

    else:
        return None

def match(word_list, expecting):
    if word_list:
        word = word_list.pop(0)

        if word[0] == expecting:
            return word
        else:
            return None

def skip(word_list, word_type):
    while peek(word_list) == word_type:
        match(word_list, word_type)

def parse_verb(word_list):
    skip(word_list, 'stop')

    if peek(word_list) == 'verb':
        return match(word_list, 'verb')
    else:
        raise ParserError("Expected a verb next.")

def parse_object(word_list):
    skip(word_list, 'stop')
    next == peek(word_list)

    if next == 'noun':
        return match(word_list, 'noun')
    if next == 'direction':
        return match(word_list, 'direction')
    else:
        raise ParserError("Expected a nour or direction next")

def pars_subject(word_list, subj):
    verb = parse_verb(word_list)
    obj = parse_object(word_list)

    return Sentence(subj, verb, obj)


def parse_sentence(word_list):
    skip(word_list, 'stop')

    if start == 'noun':
        subj = match(word_list, 'noun') 
        return parse_subject(word_list, subj)
    elif start == 'verb':
        # assume the subject is a player then
        return parse_subject(word_list,('noun', 'player'))
    else:

raise ParserError("Must start with subject, object, or verb not:%s" % start)

The Following the test script:

---------------------------------------------------------------------------------------------------------------

from nose.tools import *
from ex48.lexicon import lexicon
from ex49.ex49 import *

def test_parse_subject():      
    testsentence = "princess go east"     
    result = lexicon.scan(testsentence)     
    Sent = parse_sentence(result)     
    ResultSent = Sentence(('subject', 'princess'),            
                          ('verb', 'go'),                       
                          ('object', 'east'))     
    print ResultSent.subject     
    print ResultSent.verb     
    print ResultSent.object     
    print Sent.subject     
    print Sent.verb     
    print Sent.object     

assert_equal(Sent, ResultSent)

When i run nosetests command to execute this, it gives an error message:

PS C:\Users\rk\projects\parser> nosetests
E
======================================================================
ERROR: Failure: NameError (name 'Object' is not defined)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\nose\loader.py", line 390, in loadTestsFro
mName
    addr.filename, addr.module)
  File "C:\Python27\lib\site-packages\nose\importer.py", line 39, in importFromP
ath
    return self.importFromDir(dir_path, fqname)
  File "C:\Python27\lib\site-packages\nose\importer.py", line 86, in importFromD
ir
    mod = load_module(part_fqname, fh, filename, desc)
  File "C:\Users\rk\projects\parser\tests\ex49_test.py", line 3, in <module>
    from ex49.ex49 import *
  File "C:\Users\rk\projects\parser\ex49\ex49.py", line 8, in <module>
    class Sentence(Object):
NameError: name 'Object' is not defined

----------------------------------------------------------------------
Ran 1 test in 0.031s

FAILED (errors=1)

Object is not defined, maybe it should be object?

but still the error is there

PS C:\Users\rk\projects\parser> nosetests
E
======================================================================
ERROR: tests.ex49_test.test_parse_subject
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\nose\case.py", line 197, in runTest
    self.test(*self.arg)
  File "C:\Users\rk\projects\parser\tests\ex49_test.py", line 9, in test_parse_s
ubject
    Sent = parse_sentence(result)
  File "C:\Users\rk\projects\parser\ex49\ex49.py", line 78, in parse_sentence
    raise ParserError("Must start with subject, object, or verb not:%s" % start)

ParserError: Must start with subject, object, or verb not:direction

----------------------------------------------------------------------
Ran 1 test in 0.281s

FAILED (errors=1)
PS C:\Users\rk\projects\parser>

i found out that error is due to this:

PS C:\Users\rk\projects\parser> nosetests
E
======================================================================
ERROR: tests.ex49_test.test_parse_subject
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\nose\case.py", line 197, in runTest
    self.test(*self.arg)
  File "C:\Users\rk\projects\parser\tests\ex49_test.py", line 16, in test_parse_
subject
    print Sent.subject
AttributeError: 'NoneType' object has no attribute 'subject'
-------------------- >> begin captured stdout << ---------------------
princess
go
east

--------------------- >> end captured stdout << ----------------------

----------------------------------------------------------------------
Ran 1 test in 0.016s

FAILED (errors=1)
PS C:\Users\rk\projects\parser>

The sent variable in test script is not returning any value. This is the cause of error. Any suggestions on this?