import unittest
import io
import re
from unittest import mock
import math
import student_X as main #Replace student_X with your filename 
    
    
    
 

class LastCharactersTests(unittest.TestCase):

    def test_default_case(self):
        function = main.last_characters
        
        test = False
        try:
            incorrect = ""
            result = function.__doc__.strip()
            test = incorrect != result
        except:
            pass
        message = "No docstring."
        self.assertTrue(test, message)

        
        inputs = ("monkey cave", 0)
        correct = ''
        if isinstance(inputs, tuple):
            result = function(*inputs)
        else:
            result = function(inputs)
        test = result == correct
        message = "Doesn't work when the number of characters is zero."
        self.assertTrue(test, message)

        
        inputs = ("weasel", 1)
        correct = 'l'
        if isinstance(inputs, tuple):
            result = function(*inputs)
        else:
            result = function(inputs)
        test = result == correct
        message = "Doesn't work when the number of characters is 1."
        self.assertTrue(test, message)

        
        inputs = ("monkey cave", 4)
        correct = 'cave'
        if isinstance(inputs, tuple):
            result = function(*inputs)
        else:
            result = function(inputs)
        test = result == correct
        message = "Doesn't work when the number of characters is 4."
        self.assertTrue(test, message)

        
        inputs = ("monkey cave", 11)
        correct = 'monkey cave'
        if isinstance(inputs, tuple):
            result = function(*inputs)
        else:
            result = function(inputs)
        test = result == correct
        message = "Doesn't work when it's the whole string."
        self.assertTrue(test, message)
        
        
if __name__ == "__main__":
    tests = LastCharactersTests()
    tests.test_default_case()