Running pytest-qt on CircleCI

问题

I am attempting to run tests which require pytest-qt (for testing PySide2 dialogs) on CircleCI. I am getting the following error:

xdpyinfo was not found, X start can not be checked! Please install xdpyinfo!
============================= test session starts ==============================
platform linux -- Python 3.6.8, pytest-5.0.0, py-1.8.0, pluggy-0.12.0 -- /home/circleci/project-caveman/venv/bin/python3
cachedir: .pytest_cache
PySide2 5.13.0 -- Qt runtime 5.13.0 -- Qt compiled 5.13.0
rootdir: /home/circleci/project-caveman
plugins: cov-2.7.1, xvfb-1.2.0, qt-3.2.2
collected 1 item                                                               

tests/test_main.py::test_label_change_on_button_press Fatal Python error: Aborted

Aborted (core dumped)
Exited with code 134

And I am using this configuration file:

version: 2
jobs:
  build:
    working_directory: ~/project-caveman
    docker:
      - image: circleci/python:3.6.8-stretch
    steps:
      - checkout

      # Dependencies
      - restore_cache:
          keys:
            - venv-{{ .Branch }}-{{ checksum "setup.py" }}
            - venv-{{ .Branch }}-
            - venv-
      - run:
          name: Install dependencies
          command: |
            python3 -m venv venv
            . venv/bin/activate
            pip install -e .[test] --progress-bar off
      - save_cache:
          key: venv-{{ .Branch }}-{{ checksum "setup.py" }}
          paths:
            - "venv"

      # Tests
      - run:
          name: Pytest
          command: |
            mkdir test-reports
            . venv/bin/activate
            xvfb-run -a pytest -s -v --doctest-modules --junitxml test-reports/junit.xml --cov=coveralls --cov-report term-missing
      - store_test_results:
          path: test-reports
      - run:
          name: Coveralls
          command: coveralls

Any help is greatly appreciated, thanks in advance.

回答1:

I have pulled the container circleci/python:3.6.8-stretch locally, cloned your repository and tried to execute the tests, whereas I could reproduce the error.

First thing to do is to enable the debug mode for Qt runtime so it prints some info on errors. This can be done by settings the environment variable QT_DEBUG_PLUGINS:

$ QT_DEBUG_PLUGINS=1 pytest -sv

Now it's immediately clear what's missing in the container to run the tests. A snippet from the output of the above command:

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/bin/platforms" ...
Cannot load library /home/circleci/.local/lib/python3.6/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/home/circleci/.local/lib/python3.6/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so" : "Cannot load library /home/circleci/.local/lib/python3.6/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted (core dumped)

The fix for that is easy - install the libxkbcommon-x11-0 package:

$ sudo apt update && sudo apt install -y libxkbcommon-x11-0

Add this line in the CircleCI config (somewhere before the tests job, for example in the job where you install package dependencies) and the test should run fine.

Aside from that, it makes sense to set QT_DEBUG_PLUGINS=1 globally so you can react on eventual Qt runtime failures in future.