first.py

def largest_element(elements):
	pass

output

----------------------------------------------------------------------
Ran 4 tests in 0.006s

FAILED (failures=3)
test_largest_element (test_first.Test_TestIncrementDecrement) ... FAIL
NoneType: None
test_largest_element_negatives (test_first.Test_TestIncrementDecrement) ... FAIL
NoneType: None
test_largest_element_single (test_first.Test_TestIncrementDecrement) ... FAIL
NoneType: None
test_largest_element_void (test_first.Test_TestIncrementDecrement) ... ok

======================================================================
FAIL: test_largest_element (test_first.Test_TestIncrementDecrement)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/alan/Documentos/Nes/01/test_first.py", line 6, in test_largest_element
    self.assertEqual(first.largest_element([1, -1, 2, 4]), 4)
AssertionError: None != 4

======================================================================
FAIL: test_largest_element_negatives (test_first.Test_TestIncrementDecrement)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/alan/Documentos/Nes/01/test_first.py", line 8, in test_largest_element_negatives
    self.assertEqual(first.largest_element([-1, -1, -2, -4]), -1)
AssertionError: None != -1

======================================================================
FAIL: test_largest_element_single (test_first.Test_TestIncrementDecrement)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/alan/Documentos/Nes/01/test_first.py", line 10, in test_largest_element_single
    self.assertEqual(first.largest_element([0]), 0)
AssertionError: None != 0

----------------------------------------------------------------------
Ran 4 tests in 0.003s

FAILED (failures=3)

test_first.py

import unittest
import first

class Test_TestIncrementDecrement(unittest.TestCase):
    def test_largest_element(self):
        self.assertEqual(first.largest_element([1, -1, 2, 4]), 4)

    def test_largest_element_negatives(self):
        self.assertEqual(first.largest_element([-1, -1, -2, -4]), -1)
        
    def test_largest_element_single(self):
        self.assertEqual(first.largest_element([0]), 0)
        
    def test_largest_element_void(self):
        self.assertEqual(first.largest_element([]), None)


if __name__ == '__main__':
    unittest.main()