How to reset qapp_args for each test class? about pytest-qt HOT 6 CLOSED

it might not be possible to change the qapp fixture per test class

If this is true, one should try do this differently. For example using the mocker fixture:

Note that you can simplify this a bit by using monkeypatch which is built into pytest:

class Test1:
    def test_pos_args(self, qapp, monkeypatch):
        monkeypatch.setattr(QCommandLineParser, "positionalArguments", lambda: ["a1"])
        args = get_positional_args(qapp)
        assert len(args) == 1

class Test2:
    def test_pos_args(self, qapp, monkeypatch):
        monkeypatch.setattr(
            QCommandLineParser,
            "positionalArguments",
            lambda: ["a1"], ["a2"]
        )
        args = get_positional_args(qapp)
        assert len(args) == 2

from pytest-qt.

It seems like it is using the qapp_args() defined in the Test1 class instead.

I think the fixtures should have scope class and not session? But if I change the scope to class I get another error:
ScopeMismatch: You tried to access the class scoped fixture qapp_args with a session scoped request object:

from pytest-qt.

ScopeMismatch: You tried to access the class scoped fixture qapp_args with a session scoped request object

I think it might not be possible to change the qapp fixture per test class, since the fixture creates a QApplication instance

or retrieves a previously stored instance

As I understand, the command line arguments are passed to the QApplication constructor and cannot be modified thereafter, also it not possible to destroy a QApplication object within an app and create a new one (passing different command line parameters to the constructor), see https://forum.qt.io/topic/110418/how-to-destroy-a-singleton-and-then-create-a-new-one/11

from pytest-qt.

it might not be possible to change the qapp fixture per test class

If this is true, one should try do this differently. For example using the mocker fixture:

#  ... code above this line is the same as before
pytest.fixture(scope="session")
def qapp_args():
    # Needed this to avoid returning the emtpy "[]" default value which will cause QCommandLineParser.process(app)
    # to abort with error: argument list cannot be empty, it should contain at least the executable name
    return ["prog_name"]

class Test1:
    def test_pos_args(self, qapp, mocker):
        cmd_line_args = ["a1"]
        mocker.patch(
            __name__ + ".QCommandLineParser.positionalArguments",
            return_value=cmd_line_args,
        )
        args = get_positional_args(qapp)
        assert len(args) == 1

class Test2:
    def test_pos_args(self, qapp, mocker):
        cmd_line_args = ["a1", "a2"]
        mocker.patch(
            __name__ + ".QCommandLineParser.positionalArguments",
            return_value=cmd_line_args,
        )
        args = get_positional_args(qapp)
        assert len(args) == 2

from pytest-qt.

You got the gist of it: QApplication can only be instantiated once per process, after that you cannot really change its arguments.

If you need to test this somehow, you will probably need to restructure your code a bit and use mock.

Closing for now, I assume there is nothing actionable for pytest-qt here.

from pytest-qt.

Note that you can simplify this a bit by using monkeypatch which is built into pytest

@The-Compiler Thanks for the tip!!

from pytest-qt.