Hello.
I have some function with doctest in a file called "spam.py"
```
def egg():
"""
>>> egg()
True
"""
return True
```
I want to run doctest using pytest:
``pytest spam.py::egg --doctest-modules``
But it doesn't work:
==no tests ran in 0.05s ==
It seems that I can't run doctest for any particular function: I can run it
only for the whole directory.
Is this behavior intentional or a bug?
Thank you.
Ilya.
