The context

I try to create an integration test for an graphical user interface (GUI) written with Qt5 through python3 (so using pyqt5). And I use pytest with the plugging pytest-qt to test the GUI.

I test the GUI which here is largely inspired from this question, so the command pytest -v -s runs well.

Since my repository is on Github, I use Travis-CI to perform my integration tests.

The error

However when I push on Github and so I launch the Travis tests I get at some point the following error:

Exceptions caught in Qt event loop:
________________________________________________________________________________
Traceback (most recent call last):
  File "/home/travis/build/XXXX/Test/GUI_test.py", line 29, in handle_dialog
    yes_button = messagebox.button(QtWidgets.QMessageBox.Yes)
AttributeError: 'Example' object has no attribute 'button'

MWE

I reproduce this error in a MWE with the following files that are contained in my git repository:

the GUI written in python GUI.py :

#!/usr/bin/python3
# -*- coding: utf-8 -*-
import sys

from PyQt5 import QtGui, QtCore, QtWidgets

from PyQt5.QtWidgets import *
from PyQt5.QtCore import QCoreApplication, Qt, QObject
from PyQt5.QtGui import QIcon


class Example(QMainWindow):
    def __init__(self, parent = None):
        super().__init__()
        self.initUI(self)

    def initUI(self, MainWindow):
        # centralwidget
        MainWindow.resize(346, 193)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        # The Action to quit
        self.toolb_action_Exit = QAction(QIcon('exit.png'), 'Exit', self)
        self.toolb_action_Exit.setShortcut('Ctrl+Q')
        self.toolb_action_Exit.triggered.connect(self.close)

        # The Button
        self.btn_prt = QtWidgets.QPushButton(self.centralwidget)
        self.btn_prt.setGeometry(QtCore.QRect(120, 20, 89, 25))
        self.btn_prt.clicked.connect(lambda: self.doPrint() )
        self.btn_quit = QtWidgets.QPushButton(self.centralwidget)
        self.btn_quit.setGeometry(QtCore.QRect(220, 20, 89, 25))
        self.btn_quit.clicked.connect(lambda: self.close() )

        # The textEdit
        self.textEdit = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit.setGeometry(QtCore.QRect(10, 60, 321, 81))

        # Show the frame
        MainWindow.setCentralWidget(self.centralwidget)
        self.show()

    def doPrint(self):
        print('TEST doPrint')

    def closeEvent(self, event):
        # Ask a question before to quit.
        self.replyClosing = QMessageBox.question(self, 'Message',
            "Are you sure to quit?", QMessageBox.Yes |
            QMessageBox.No, QMessageBox.No)

        if self.replyClosing == QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()


def main_GUI():
    print('start')
    app = QApplication(sys.argv)
    imageViewer = Example()
    return app, imageViewer


if __name__ == '__main__':
    app, imageViewer =main_GUI()
    rc= app.exec_()
    print('App end is exit code {}'.format(rc))
    sys.exit(rc)

the file use by pytest to create unittest GUI_test.py :

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import os, sys 

from PyQt5 import QtGui, QtCore, QtWidgets, QtTest
from PyQt5.QtWidgets import *
from PyQt5.QtCore import QCoreApplication, Qt, QObject

import pytest
import warnings
from pytestqt.plugin import QtBot, capture_exceptions
import mock

@pytest.fixture(scope="module")
def Viewer(request):
    print("  SETUP GUI")
    GUI= __import__('GUI')
    app, imageViewer = GUI.main_GUI()
    with capture_exceptions() as exceptions:
        qtbotbis = QtBot(app)
        QtTest.QTest.qWait(0.5 *1000)
        yield app, imageViewer, qtbotbis

        ######### EXIT ##########
        app.quitOnLastWindowClosed()
        def handle_dialog():
            messagebox = QtWidgets.QApplication.activeWindow()
            yes_button = messagebox.button(QtWidgets.QMessageBox.Yes)
            qtbotbis.mouseClick(yes_button, QtCore.Qt.LeftButton, delay=1)
        QtCore.QTimer.singleShot(100, handle_dialog)
        qtbotbis.mouseClick(imageViewer.btn_quit, QtCore.Qt.LeftButton, delay=1)
        assert imageViewer.isHidden()

        app.closeAllWindows()
        app.quit()
        app.exit()
        app.closingDown()
        QtTest.QTest.qWait(0.5 *1000)
        with mock.patch.object(QApplication, "exit"):
            app.exit()
            assert QApplication.exit.call_count == 1
            print("[Notice] So a mock.patch is used to count if the signal is emitted.")
        print("  TEARDOWN GUI")


class Test_GUI_CXS() : 

    def test_buttons(self, Viewer, caplog):
        app, mainWindow, qtbot = Viewer

        qtbot.mouseClick( mainWindow.btn_prt, QtCore.Qt.LeftButton )

The file to control the travis job .travis.yml (which is able to deal with graphical windows according to the documentation p32):

language: python
python:
  - "3.7"

sudo: required
dist: bionic

jobs:
  include:
  - stage: test
    name: PyTest-GUI
    before_install:
    - python -m pip install --upgrade pip
    - pip install -r ./requirement.txt
    - sudo apt-get install -y libdbus-1-3 libxkbcommon-x11-0 dzen2
    install:
      - "export DISPLAY=:99.0"
      - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1920x1200x24 -ac+extension GLX +render -noreset"
      - sleep 3
    before_script:
      - "herbstluftwm &"
      - sleep 1
    script:
    - pytest -s -v ./GUI_test.py
    addons:
      apt:
        packages:
        - x11-utils
        - libxkbcommon-x11-0
        - herbstluftwm
        - xvfb
    services: xvfb

and the file containning the required libraries requirement.txt :

pyqt5
mock
pytest
pytest-qt

Other attempts

I try to run the travis job in a debug mode. So after connecting through a ssh the install all the dependencies, I tryed to run the command pytest and get the same error.

However, if I do herbstluftwm & then pytest the test runs well and no error appear. Therefore, I assume that there is a problem with the command herbstluftwm & on the normal travis job, but I do not know how to solve it.

Any tips or help is welcomed !

In my previous answer I chose 100ms empirically but depending on the resources that time may vary so that I don't have to place a time that can fail and implemented a function that will run every T seconds until I find the QMessageBox.

#!/usr/bin/env python3
# -*- coding: utf-8 -*-


from PyQt5 import QtCore, QtWidgets, QtTest

import mock

import pytest
from pytestqt.plugin import QtBot, capture_exceptions


def get_messagebox(t=100, max_attemps=-1):
    messagebox = None
    attempt = 0
    loop = QtCore.QEventLoop()

    def on_timeout():
        nonlocal attempt, messagebox

        attempt += 1
        active_window = QtWidgets.QApplication.activeWindow()

        if isinstance(active_window, QtWidgets.QMessageBox):
            messagebox = active_window
            loop.quit()
        elif max_attemps > 0:
            if attempt > max_attemps:
                loop.quit()
        else:
            QtCore.QTimer.singleShot(t, on_timeout)

    QtCore.QTimer.singleShot(t, on_timeout)
    loop.exec_()
    return messagebox


@pytest.fixture(scope="module")
def Viewer(request):
    print("  SETUP GUI")
    GUI = __import__("GUI")
    app, imageViewer = GUI.main_GUI()
    with capture_exceptions():
        qtbotbis = QtBot(app)
        QtTest.QTest.qWait(0.5 * 1000)
        yield app, imageViewer, qtbotbis

        app.quitOnLastWindowClosed()

        def handle_dialog():
            messagebox = get_messagebox()
            yes_button = messagebox.button(QtWidgets.QMessageBox.Yes)
            qtbotbis.mouseClick(yes_button, QtCore.Qt.LeftButton, delay=1)

        QtCore.QTimer.singleShot(10, handle_dialog)
        qtbotbis.mouseClick(imageViewer.btn_quit, QtCore.Qt.LeftButton, delay=1)
        assert imageViewer.isHidden()

        app.closeAllWindows()
        app.quit()
        app.exit()
        app.closingDown()
        QtTest.QTest.qWait(0.5 * 1000)
        with mock.patch.object(QtWidgets.QApplication, "exit"):
            app.exit()
            assert QtWidgets.QApplication.exit.call_count == 1
            print("[Notice] So a mock.patch is used to count if the signal is emitted.")
        print("  TEARDOWN GUI")


class Test_GUI_CXS:
    def test_buttons(self, Viewer, caplog):
        app, mainWindow, qtbot = Viewer

        qtbot.mouseClick(mainWindow.btn_prt, QtCore.Qt.LeftButton)

On the other hand to do my test in travis only the following configuration is necessary:

language: python
python:
  - "3.7"

dist: bionic

jobs:
  include:
    - stage: test
      name: PyTest-GUI
      before_script:
        - python -m pip install --upgrade pip
        - pip install -r ./requirement.txt
      script: 
        - pytest -s -v ./GUI_test.py
      addons:
        apt:
          packages:
            - libxkbcommon-x11-0
      services:
        - xvfb

Considering the above passes the test: