Running py.test inside Dockerfile

Question

I have this Dockerfile that contains a line RUN py.test -vv.

FROM bitnami/python:3.6-prod
#MORE DIRECTIVES
RUN py.test -vv
COPY . /files
WORKDIR /files
EXPOSE 8080

When I run docker-compose build, I am getting this error.

Step 16/21 : RUN py.test -vv
 ---> Running in 5b3f55f10025
============================= test session starts ==============================
platform linux -- Python 3.6.9, pytest-5.2.1, py-1.8.0, pluggy-0.13.0 -- /opt/bitnami/python/bin/python
cachedir: .pytest_cache
rootdir: /
plugins: ordering-0.6, cov-2.8.1, docker-compose-3.1.2, celery-4.3.0
collecting ... collected 0 items / 1 errors

==================================== ERRORS ====================================
________________________ ERROR collecting test session _________________________
opt/bitnami/python/lib/python3.6/site-packages/_pytest/config/__init__.py:456: in _importconftest
    return self._conftestpath2mod[key]
E   KeyError: PosixPath('/opt/bitnami/python/lib/python3.6/site-packages/matplotlib/tests/conftest.py')

During handling of the above exception, another exception occurred:
opt/bitnami/python/lib/python3.6/site-packages/_pytest/config/__init__.py:462: in _importconftest
    mod = conftestpath.pyimport()
opt/bitnami/python/lib/python3.6/site-packages/py/_path/local.py:701: in pyimport
    __import__(modname)
opt/bitnami/python/lib/python3.6/site-packages/matplotlib/tests/__init__.py:16: in <module>
    'The baseline image directory does not exist. '
E   OSError: The baseline image directory does not exist. This is most likely because the test data is not installed. You may need to install matplotlib from source to get the test data.

During handling of the above exception, another exception occurred:
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:377: in visit
    for x in Visitor(fil, rec, ignore, bf, sort).gen(self):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:429: in gen
    for p in self.gen(subdir):
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:418: in gen
    dirs = self.optsort([p for p in entries
opt/bitnami/python/lib/python3.6/site-packages/py/_path/common.py:419: in <listcomp>
    if p.check(dir=1) and (rec is None or rec(p))])
opt/bitnami/python/lib/python3.6/site-packages/_pytest/main.py:606: in _recurse
    ihook = self.gethookproxy(dirpath)
opt/bitnami/python/lib/python3.6/site-packages/_pytest/main.py:424: in gethookproxy
    my_conftestmodules = pm._getconftestmodules(fspath)
opt/bitnami/python/lib/python3.6/site-packages/_pytest/config/__init__.py:434: in _getconftestmodules
    mod = self._importconftest(conftestpath)
opt/bitnami/python/lib/python3.6/site-packages/_pytest/config/__init__.py:470: in _importconftest
    raise ConftestImportFailure(conftestpath, sys.exc_info())
E   _pytest.config.ConftestImportFailure: (local('/opt/bitnami/python/lib/python3.6/site-packages/matplotlib/tests/conftest.py'), (<class 'OSError'>, OSError('The baseline image directory does not exist. This is most likely because the test data is not installed. You may need to install matplotlib from source to get the test data.',), <traceback object at 0x7f814caaef88>))
!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!
============================== 1 error in 11.83s ===============================
ERROR: Service 'testproject' failed to build: The command '/bin/sh -c py.test -vv' returned a non-zero code: 2

I have tried adding pip install matplotlib in the Dockerfile but I am still getting the same error.

I have a NodeJS app before that was also Dockerized that has some tests on it using mocha and putting RUN mocha inside the Dockerfile works fine. I'm not sure what's the issue here in Python.

Answer 1

I feel that the issue here is because pytest is not pre-installed in python. Hence you have to add steps for pytest installation in the docker container. Personally I have been running this by using a seperate dockerfile for pytest, which is using for installing and setting the ENTRYPOINT as pytest.

I have attached the docker-compose.yaml, dockerfile and pytest.dockerfile for you reference. Alternatively you can directly mention the pytest installation steps in the .yaml file/dockerfile itself as you are not having any other services to be added and to avoid the additional dockerfile. This set-up is runing perfectly for me for running Selenium-pytest test automation using docker containers. Please try this and let us know the feedback.

version: '3.7'
services:
  test:
    volumes:
      - .:/files 
    build: 
      context: .
      dockerfile: pytest.dockerfile

docker-compose.yaml

FROM python:3.7-alpine
MAINTAINER xyz

ADD . /files
WORKDIR /files

ENV PYTHONDONTWRITEBYTECODE=true
EXPOSE 4444

dockerfile. The option to expose the port is again optional here.

FROM python:3.7-alpine
MAINTAINER xyz

RUN pip install pytest

ENTRYPOINT [ "pytest" ]

pytest.dockerfile