As noted in discussion we usually reserve `assert` for standard tests (functions named `test_foo()` if files named `test_foo.py`).

Doctests should foremost be examples showing users how the function operates in a nicely selected set of contexts.  Doctests are user-facing, tests are developer facing.

Nosetests does allow us to leverage doctests as normal tests though.  It runs the example and then compares the result it gets against the string that's provided below this line.  So this doctest could equivalently be written as 

```Python
>>> fnone(sorted, default=[])([5, 1, 2]) == sorted([5, 1, 2])
True
```

However it is probably nicer on the user to change it to the following:

```Python
>>> sorted2 = fnone(sorted, default=[])

>>> sorted2([5, 1, 2])
[1, 2, 5]
>>> sorted2()
[]
```