[TIP] pytest: mocking module imports

[Zhi An Ng]

Hi,
feels like the patch should be like this:

<test_liba.py>
@patch('liba.ClassB')

overwrite the ClassB that was imported in liba.py

*note liba.ClassB might not be the right complete path, you might have some
folders you need to traverse or sth, but that's the general idea.

Best,
Zhi An

On Fri, Apr 17, 2015 at 3:23 PM, Vinicius Kwiecien Ruoso <
vinicius.ruoso at gmail.com> wrote:

> Hi!
>
> Thanks for your answer. Unfortunately, this does not work for me.
> libB is not importable during the test, and at some point the test try
> to import it.
>
> Let me show a real minimal example:
> ├── src
> │   └── mylib
> │       ├── __init__.py
> │       ├── liba.py
> └── test
>     └── mylib
>         ├── conftest.py
>         └── test_liba.py
>
> 8<---------
> <liba.py>
> from mylibB.libb import ClassB
>
> class ClassA(ClassB):
>     pass
>
> <conftest.py>
> import os
> import sys
>
> _src_path = os.path.join(os.path.dirname(__file__), '..', '..', 'src')
> sys.path.insert(0, os.path.abspath(_src_path))
>
> <test_liba.py>
> from mock import patch
>
> @patch('mylibB.libb.ClassB')
> def test_classa_instance(mock_classB):
>     print mock_classB
> 8<---------
>
> This fails with: "ImportError: No module named mylibB" while executing
> the patch code.
>
> My real intent on the test_liba.py file was (and for that to work, I
> need to mock libb module import at the conftest.py file):
>
> import mylib.liba
>
> def test_classa_instance(mock_classB):
>     print mylib.liba.ClassA()
>
>
> Attached you may find this file structure if you want to run it.
>
> Just as a note, I'm using Python 2.6 right now. I intend to support
> Python 2.7, but not 3.x at this time.
>
> Thanks again!
> Vinicius
>
> 2015-04-17 14:47 GMT-03:00 Zhi An Ng <ngzhian at gmail.com>:
> > Hi,
> > I believe you can mock out ClassY as such:
> >
> > @patch('liB.ClassY')
> > def test_unit_test(self):
> >     stuff
> >
> >
> > More info:
> > https://docs.python.org/3.3/library/unittest.mock.html#quick-guide
> >
> > Best,
> > Zhi An
> >
> > On Fri, Apr 17, 2015 at 1:35 PM, Vinicius Kwiecien Ruoso
> > <vinicius.ruoso at gmail.com> wrote:
> >>
> >> Hi!
> >>
> >> I've been using pytest and it is great. There is just one thing that
> >> I'm not satisfied with the way I've implemented, that is module level
> >> moking.
> >>
> >> My scenario is as follows: libA and libB where libA depends on libB
> >> (uses class definition as superclass). Let's assume this code:
> >>
> >> <libA.py>
> >> from libB import ClassY
> >>
> >> class ClassX(ClassY):
> >>    pass
> >>
> >> <libB.py>
> >> class ClassY(object):
> >>    pass
> >>
> >> Those modules live on different packages/repositories. LibB can be
> >> unit tested just fine, but we need to mock libB module to allow libA
> >> to be unit tested (libB won't be available in the moment of the test).
> >>
> >> In a conftest.py file in the tests directory of libA, I've managed to
> >> mock the module import by mocking sys.modules dictionary, but I did
> >> this at the module (global) scope. I was not able to do it with any
> >> hook (like pytest_configure), because the tests files are imported
> >> before the hook is called. So a test_libA.py file with "import libA"
> >> would cause the test to fail.
> >>
> >> Am I doing something wrong or is this really the way to go?
> >>
> >> Greetings,
> >> Vinicius
> >>
> >> _______________________________________________
> >> testing-in-python mailing list
> >> testing-in-python at lists.idyll.org
> >> http://lists.idyll.org/listinfo/testing-in-python
> >
> >
>
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