3. Testing and Debugging Jupyter Notebooks

3.1. Running Example

def add(a, b):
    """Return the sum of a and b."""
    sum = a
    return sum

3.2. Doctest

def add(a, b):
    """Return the sum of a and b.

    >>> add(2, 2)
    4
    """
    sum = a
    return sum

import doctest
doctest.testmod(verbose=True)

Trying:
    add(2, 2)
Expecting:
    4
**********************************************************************
File "__main__", line 4, in __main__.add
Failed example:
    add(2, 2)
Expected:
    4
Got:
    2
1 items had no tests:
    __main__
**********************************************************************
1 items had failures:
   1 of   1 in __main__.add
1 tests in 2 items.
0 passed and 1 failed.
***Test Failed*** 1 failures.

TestResults(failed=1, attempted=1)

3.3. Unittest

import unittest


class TestNotebook(unittest.TestCase):

    def test_add(self):
        self.assertEqual(add(2, 2), 5)

unittest.main(argv=[''], verbosity=2, exit=False)

test_add (__main__.TestNotebook) ... FAIL

======================================================================
FAIL: test_add (__main__.TestNotebook)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "<ipython-input-4-4ac71e015a29>", line 7, in test_add
    self.assertEqual(add(2, 2), 5)
AssertionError: 2 != 5

----------------------------------------------------------------------
Ran 1 test in 0.003s

FAILED (failures=1)

<unittest.main.TestProgram at 0x7f9fdcd4d4a8>

3.4. Debugging a Failed Test

def add(a, b):
    """Return the sum of a and b.

    >>> add(2, 2)
    4
    """
    sum = a
    import pdb; pdb.set_trace()
    return sum

import doctest
doctest.testmod(verbose=True)

Trying:
    add(2, 2)
Expecting:
    4
> <ipython-input-4-c9a7cd1fc273>(9)add()
-> return sum
(Pdb) sum
2
(Pdb) q
**********************************************************************
File "__main__", line 4, in __main__.add
Failed example:
    add(2, 2)
Exception raised:
    Traceback (most recent call last):
      File "/usr/lib/python3.6/doctest.py", line 1330, in __run
        compileflags, 1), test.globs)
      File "<doctest __main__.add[0]>", line 1, in <module>
        add(2, 2)
      File "<ipython-input-4-c9a7cd1fc273>", line 9, in add
        return sum
      File "<ipython-input-4-c9a7cd1fc273>", line 9, in add
        return sum
      File "/usr/lib/python3.6/doctest.py", line 379, in trace_dispatch
        return pdb.Pdb.trace_dispatch(self, *args)
      File "/usr/lib/python3.6/bdb.py", line 51, in trace_dispatch
        return self.dispatch_line(frame)
      File "/usr/lib/python3.6/bdb.py", line 70, in dispatch_line
        if self.quitting: raise BdbQuit
    bdb.BdbQuit
1 items had no tests:
    __main__
**********************************************************************
1 items had failures:
   1 of   1 in __main__.add
1 tests in 2 items.
0 passed and 1 failed.
***Test Failed*** 1 failures.

TestResults(failed=1, attempted=1)