I am trying to test a function that creates a message exchange graph from IRC chat logs. I am having trouble trying to mock the dependencies. The function makes use of util module, a lot of which takes input and returns an output. The problem is that these utils functions are being called multiple times inside for loops and if-conditionals. How do I specify multiple returns based on output? I would like to know how to unit-test functions similar to these.

I have been using python standard unittest and mock libraries.

Source of the code: IRCLogParser

def message_number_graph(log_dict, nicks, nick_same_list,DAY_BY_DAY_ANALYSIS=False):     """      Creates a directed graph     with each node representing an IRC user     and each directed edge has a weight which      mentions the number messages sent and recieved by that user      in the selected time frame.  Args:     log_dict (dict): with key as dateTime.date object and value as {"data":datalist,"channel_name":channels name}     nicks(list): list of all the nicks     nick_same_list(list): list of lists mentioning nicks which belong to same users Returns:    message_number_graph (nx graph object) """ message_number_day_list = [] conversations=[[0] for i in range(config.MAX_EXPECTED_DIFF_NICKS)] aggregate_message_number_graph = nx.DiGraph()  #graph with multiple directed edges between clients used  G = util.to_graph(nick_same_list) conn_comp_list = list(connected_components(G))  util.create_connected_nick_list(conn_comp_list)  def msg_no_analysis_helper(rec_list, corrected_nick, nick, conn_comp_list,conversations,today_conversation):     for receiver in rec_list:         if(receiver == nick):             if(corrected_nick != nick):                                                  nick_receiver = ''                 nick_receiver = util.get_nick_sen_rec(config.MAX_EXPECTED_DIFF_NICKS, nick, conn_comp_list, nick_receiver)                      if DAY_BY_DAY_ANALYSIS:                     today_conversation = util.extend_conversation_list(nick_sender, nick_receiver, today_conversation)                 else:                     conversations = util.extend_conversation_list(nick_sender, nick_receiver, conversations)  def message_no_add_egde(message_graph, conversation):     for index in xrange(config.MAX_EXPECTED_DIFF_NICKS):         if(len(conversation[index]) == 3 and conversation[index][0] >= config.THRESHOLD_MESSAGE_NUMBER_GRAPH):             if len(conversation[index][1]) >= config.MINIMUM_NICK_LENGTH and len(conversation[index][2]) >= config.MINIMUM_NICK_LENGTH:                 message_graph.add_edge(util.get_nick_representative(nicks, nick_same_list, conversation[index][1]), util.get_nick_representative(nicks, nick_same_list, conversation[index][2]), weight=conversation[index][0])     return message_graph   for day_content_all_channels in log_dict.values():     for day_content in day_content_all_channels:         day_log = day_content["log_data"]         today_conversation = [[0] for i in range(config.MAX_EXPECTED_DIFF_NICKS)]         for line in day_log:             flag_comma = 0              if(util.check_if_msg_line (line)):                 parsed_nick = re.search(r"\<(.*?)\>", line)                 corrected_nick = util.correctLastCharCR(parsed_nick.group(0)[1:-1])                 nick_sender = ""                 nick_receiver = ""                                     nick_sender = util.get_nick_sen_rec(config.MAX_EXPECTED_DIFF_NICKS, corrected_nick, conn_comp_list, nick_sender)                          for nick in nicks:                     rec_list = [e.strip() for e in line.split(':')]                     util.rec_list_splice(rec_list)                     if not rec_list[1]:                         break                                             rec_list = util.correct_last_char_list(rec_list)                            msg_no_analysis_helper(rec_list, corrected_nick, nick, conn_comp_list, conversations,today_conversation)                      if "," in rec_list[1]:                         flag_comma = 1                         rec_list_2=[e.strip() for e in rec_list[1].split(',')]                         for i in xrange(0,len(rec_list_2)):                             if(rec_list_2[i]):                                 rec_list_2[i] = util.correctLastCharCR(rec_list_2[i])                                                     msg_no_analysis_helper(rec_list_2, corrected_nick, nick, conn_comp_list, conversations, today_conversation)                                      if(flag_comma == 0):                         rec = line[line.find(">")+1:line.find(", ")]                         rec = rec[1:]                         rec = util.correctLastCharCR(rec)                         if(rec == nick):                             if(corrected_nick != nick):                                                                    nick_receiver = nick_receiver_from_conn_comp(nick, conn_comp_list)                  if DAY_BY_DAY_ANALYSIS:             today_message_number_graph = nx.DiGraph()             today_message_number_graph = message_no_add_egde(today_message_number_graph, today_conversation)                             year, month, day = util.get_year_month_day(day_content)             message_number_day_list.append([today_message_number_graph, year+'-'+month+'-'+day])  print "\nBuilding graph object with EDGE WEIGHT THRESHOLD:", config.THRESHOLD_MESSAGE_NUMBER_GRAPH  if not DAY_BY_DAY_ANALYSIS:     aggregate_message_number_graph = message_no_add_egde(aggregate_message_number_graph, conversations)   if config.DEBUGGER:     print "========> 30 on " + str(len(conversations)) + " conversations"     print conversations[:30]  if DAY_BY_DAY_ANALYSIS:     return message_number_day_list else:     return aggregate_message_number_graph