How to handle modal dialog in pytest-qt without mocking the dialog

[Nagendraprasath-R]

I am using pytest-qt to automate the testing of a PyQt GUI. The dialogs need to be handled as a part of the testing(dialogs should not be mocked).

For example, file dialog that comes after a button-click has to be handled. There are 2 problems

1. After the button click command, the program control goes to the event handler and not to the next line where I can try to send mouseclick/keystrokes to the dialog.

2. Since the QDialog is not added to the main widget, it is not being listed among the children of the main widget. So how to get the reference of the QDialog?

I tried multi-threading but that didn't work, later I found that QObjects are not thread-safe.

def test_filedialog(qtbot, window):
    qtbot.mouseClick(window.browseButton, QtCore.Qt.LeftButton, delay=1)    
    print("After mouse click")    
    #This is where I need to get the reference of QDialog and handle it

[nicoddemus]

On way is to setup a timer which triggers a slot after a few miliseconds, giving it a chance for the dialog to show up:

def test_filedialog(qtbot, window):
    def handle_dialog():
        # get a reference to the dialog and handle it here
    QTimer.singleShot(500, handle_dialog)
    qtbot.mouseClick(window.browseButton, QtCore.Qt.LeftButton, delay=1)    

This method unfortunately is not very reliable because you might be unlucky if the dialog takes more than 500ms to show up (due to a spike in CPU usage by another process for example).

Is this dialog you trying to mock your own or Qt's?

[Nagendraprasath-R]

Thanks, @nicoddemus. This works and it solves a part of my issue 👍

Is there any way to find the reference of a dialog when it is not added to any parent control? Else would you suggest to add the dialog as a child to any other control? I guess this might help in making the dialog handling more reliable as I could wait in handle_dialog function until I get the dialog's reference.

def test_filedialog(qtbot, window):
    def handle_dialog():
        # I am not able to find the reference here since the dialog is not added as a child to any parent control
    QTimer.singleShot(500, handle_dialog)
    qtbot.mouseClick(window.browseButton, QtCore.Qt.LeftButton, delay=1) 

Is this dialog you trying to mock your own or Qt's?

I am trying to handle QFileDialog and some custom QDialog pop-ups.

[nicoddemus]

Is there any way to find the reference of a dialog when it is not added to any parent control? Else would you suggest to add the dialog as a child to any other control?

On way that I've accomplished this is to keep the reference to the dialog somewhere, for testing only. Then you can trigger your event in the next iteration of the event loop by passing 0 timeout to the timer:

class MyWindow(QWidget):


    def on_browse_button(self):
        self._test_dialog = QFileDialog(...)
        try:
            # do something with dialog
        finally:
            self._test_dialog = None
    

def test_filedialog(qtbot, window):
    def handle_dialog():
        while window._test_dialog is None:
            qApp.processEvents()
        # handle dialog now
    QTimer.singleShot(0, handle_dialog)
    qtbot.mouseClick(window.browseButton, QtCore.Qt.LeftButton, delay=1) 

I think this small hack is a small enough price for the reliability it brings to the table.

[Nagendraprasath-R]

@nicoddemus, It works fine with a small change :)
A minimum timeout is needed before the timer triggers handle_dialog slot in order to execute the next line that performs mouseclick which launces the file dialog.

    QTimer.singleShot(100, handle_dialog)
    qtbot.mouseClick(window.browseButton, QtCore.Qt.LeftButton, delay=1) 

Also, in some cases, I thought it might be better to check the visibility of the dialog using isVisible() method rather than creating a new instance every time.

def test_filedialog(qtbot, window):
    def handle_dialog():
        while not window._test_dialog.isVisible():
            QtGui.QApplication.processEvents()
        # handle dialog now

It would be great if there is an example for dialog hanlding without mocking it.

Thanks a lot, @nicoddemus for this solution!! :)

[nicoddemus]

Thanks! I would love a PR updating the docs with an example like this one.

Please close the issue if you don't have further questions. 👍

[Nagendraprasath-R]

Hi @nicoddemus, I have another small query. In the above method, the reference of the dialog is stored in a data member of some class, which is used to interact with the dialog., Is there any way to find the reference of the dialog when it is not stored?
I have tried QtGui.QApplication.topLevelWidgets(), QtGui.QApplication.activeModalWidget() but I could not find it among them.

[nicoddemus]

I don't know, it should be.

But I find that just storing the reference for tests is reliable and a small wart that is worth in the end.

[Nagendraprasath-R]

Sure, @nicoddemus. Thank you.

[christinab12]

Hi,

Thanks for the useful tips here @nicoddemus and @Nagendraprasath-R . I'm also writing some tests for my PyQt application and have come across this issue while trying to deal with QFileDialog.

I tried your solution, but the File Dialog still hangs open when I run the test until the user interacts. I wonder, what did you mean to do in the try statement of your on_browse_button (at the # do something with dialog comment)?

My code looks like this:

def on_button_clicked(self):

      self.fd = QFileDialog()
      try:
          self.fd.setFileMode(QFileDialog.Directory)
          if self.fd.exec_():
              self.app.data_path = self.fd.selectedFiles()[0]
          self.textbox.setText(self.app.eval_data_path)
      finally:
          self.fd = None

So, I guess self.fd is never set to None. Any ideas how I could deal with this?

Many thanks :)