$ python fizzbuzz_test.py 
..F
======================================================================
FAIL: test_FizzBuzz_de3_retorna_fizz (__main__.TestFizzBuzz)
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Traceback (most recent call last):
  File "fizzbuzz_test.py", line 15, in test_FizzBuzz_de3_retorna_fizz
    self.assertEqual(FizzBuzz(3), "fizz")
AssertionError: 3 != 'fizz'

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Ran 3 tests in 0.000s

FAILED (failures=1)