# Tutorial

`pytest-qt` registers a new fixture named `qtbot`, which acts as bot in the sense that it can send keyboard and mouse events to any widgets being tested. This way, the programmer can simulate user interaction while checking if GUI controls are behaving in the expected manner.

To illustrate that, consider a widget constructed to allow the user to find files in a given directory inside an application.

It is a very simple dialog, where the user enters a standard file mask, optionally enters file text to search for and a button to browse for the desired directory. Its source code is available here,

To test this widget’s basic functionality, create a test function:

    def test_basic_search(qtbot, tmp_path):
        """
        test to ensure basic find files functionality is working.
        """
        tmp_path.joinpath("video1.avi").touch()
        tmp_path.joinpath("video1.srt").touch()

        tmp_path.joinpath("video2.avi").touch()
        tmp_path.joinpath("video2.srt").touch()

Here the first parameter indicates that we will be using a `qtbot` fixture to control our widget.

Note

It is not necessary to create a QApplication instance, since the `qtbot` fixture will do this for you. The `QApplication` object is accessible through the qapp fixture that returns a pointer equivalent to the global `qApp` pointer.

The other parameter is pytest’s standard tmpdir that we use to create some files that will be used during our test.

Now we create the widget to test and register it:

    window = Window()
    window.show()
    qtbot.addWidget(window)

Tip

Registering widgets is not required, but recommended because it will ensure those widgets get properly closed after each test is done.

Now we can interact with the widgets directly:

    window.fileComboBox.clear()
    window.fileComboBox.setCurrentText("*.avi")

    window.directoryComboBox.clear()
    window.directoryComboBox.setCurrentText(str(tmp_path))

We use the `QComboBox.setCurrentText` method to change the current item selected in the combo box.

Note

In general, prefer to use a widget’s own methods to interact with it: `QComboBox.setCurrentIndex`, `QLineEdit.setText`, etc. Those methods will emit the appropriate signal, so the test will work just the same as if the user themselves have interacted with the controls.

Note that `qtbot` provides a number of methods to simulate actual interaction, for example `keyClicks`, `mouseClick`, etc. Those methods should be used only in specialized situations, for example if you are creating a custom drawing widget and want to simulate actual clicks.

For normal interactions, always prefer widget methods (`setCurrentIndex`, `setText`, etc) – `qtbot`’s methods (`keyClicks`, `mouseClick`, etc) will trigger an actual event, which will then need to be processed in the next pass of the event loop, making the test unreliable and flaky. Also some operations are hard to simulate using raw clicks, for example selecting an item on a `QComboBox`, which will need two `mouseClick` calls to simulate properly, while figuring out where to click.

We then simulate a user clicking the button:

    window.findButton.click()

Once this is done, we inspect the results widget to ensure that it contains the expected files we created earlier:

    assert window.filesTable.rowCount() == 2
    assert window.filesTable.item(0, 0).text() == "video1.avi"
    assert window.filesTable.item(1, 0).text() == "video2.avi"