Testing Using Pilot - `pilot.click()` Doesn't Have Effect On `Static` Widget

[MalayAgr]

Hi,

I am trying to write tests for the example calculator app present in the repo (at the same time, expanding it to add a few more operators). This is my CalculatorApp class:

class CalculatorApp(App):
    CSS_PATH = "calculator.css"

    viewport = var("0")
    show_ac = var(True)
    left = var(Decimal("0"))
    right = var(Decimal("0"))
    value = var("")
    operator = var("plus")

    def watch_viewport(self, value: str) -> None:
        self.query_one("#viewport", Static).update(value)

    def compute_show_ac(self) -> bool:
        return self.value in ("", "0") and self.viewport == "0"

    def watch_show_ac(self, show_ac: bool) -> None:
        self.query_one("#ac").display = show_ac
        self.query_one("#c").display = not show_ac

    def compose(self) -> ComposeResult:
        with Container(id="calculator"):
            yield Static(id="viewport")
            yield Button("AC", id="ac", variant="primary")
            yield Button("C", id="c", variant="primary")
            yield Button("+/-", id="negation", variant="primary")
            yield Button("%", id="percent", variant="primary")
            yield Button("sin(x)", id="sine", variant="warning")
            yield Button("cos(x)", id="cosine", variant="warning")
            yield Button("7", id="number-7", variant="primary")
            yield Button("8", id="number-8", variant="primary")
            yield Button("9", id="number-9", variant="primary")
            yield Button("+", id="plus", variant="warning")
            yield Button("x^y", id="exponent", variant="warning")
            yield Button("4", id="number-4", variant="primary")
            yield Button("5", id="number-5", variant="primary")
            yield Button("6", id="number-6", variant="primary")
            yield Button("-", id="minus", variant="warning")
            yield Button("ln(x)", id="logarithm", variant="warning")
            yield Button("1", id="number-1", variant="primary")
            yield Button("2", id="number-2", variant="primary")
            yield Button("3", id="number-3", variant="primary")
            yield Button("*", id="multiply", variant="warning")
            yield Button("x!", id="factorial", variant="warning")
            yield Button("0", id="number-0", variant="primary")
            yield Button(".", id="point", variant="primary")
            yield Button("÷", id="divide", variant="warning")
            yield Button("=", id="equals", variant="warning")

    def on_button_pressed(self, event: Button.Pressed) -> None:
        button_id = event.button.id

        assert button_id is not None

        if button_id.startswith("number-"):
            number = button_id.split("-")[-1]
            self.viewport = self.value = self.value.lstrip("0") + number

I wrote the following test to check that clicking the number buttons results in the calculator's display (Static(id="viewport")) accumulating digits to make a number:

async def test_number_buttons():
    async with CalculatorApp().run_test() as pilot:
        app = pilot.app

        await pilot.click("#number-1")

        display_content = app.query_one("#viewport").render()
        assert str(display_content) == "1"

        await pilot.click("#number-2")

        display_content = app.query_one("#viewport").render()
        assert str(display_content) == "12"

        await pilot.click("#number-3")

        display_content = app.query_one("#viewport").render()
        assert str(display_content) == "123"

While the GUI gets updated correctly on clicking the buttons, the test always fails since app.query_one("#viewport").render() always returns "0". I've also tried replacing app.query_one("#viewport").render() with app.query_one("#viewport", Static).render() but that hasn't helped either.

Is this supposed to happen?

Textual Diagnostics

Versions

Name	Value
Textual	0.14.0
Rich	13.3.2

Python

Name	Value
Version	3.10.9
Implementation	CPython
Compiler	GCC 11.2.0
Executable	/home/malay_agr/anaconda3/envs/spe/bin/python

Operating System

Name	Value
System	Linux
Release	5.15.0-52-generic
Version	#58-Ubuntu SMP Thu Oct 13 08:03:55 UTC 2022

Terminal

Name	Value
Terminal Application	vscode (1.76.1)
TERM	xterm-256color
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=197, height=19
legacy_windows	False
min_width	1
max_width	197
is_terminal	True
encoding	utf-8
max_height	19
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

[MalayAgr]

Update: Since then, I've implemented keyboard support for the number buttons and the test passes if I use pilot.press() instead of pilot.click(). This is the testing code with pilot.press():

async def test_number_buttons():
    async with CalculatorApp().run_test() as pilot:
        await pilot.press("1")

        display_content = pilot.app.query_one("#viewport", Static).render()
        assert str(display_content) == "1"

        await pilot.press("2")

        display_content = pilot.app.query_one("#viewport", Static).render()
        assert str(display_content) == "12"

        await pilot.press("3")

        display_content = pilot.app.query_one("#viewport", Static).render()
        assert str(display_content) == "123"

[MalayAgr]

Update: Since then, I've realized that it is possible to access class attributes like viewport, show_ac, left, right, etc. I've tried two variants of the above test with this in mind.

This one uses app.value.

async def test_number_buttons():
    async with CalculatorApp().run_test() as pilot:
        await pilot.click("#number-1")

        assert str(pilot.app.value) == "1"

        await pilot.click("#number-2")

        assert str(pilot.app.value) == "12"

        await pilot.click("#number-3")

        assert str(pilot.app.value) == "123"

This one uses app.viewport.

async def test_number_buttons():
    async with CalculatorApp().run_test() as pilot:
        await pilot.click("#number-1")

        assert str(pilot.app.viewport) == "1"

        await pilot.click("#number-2")

        assert str(pilot.app.viewport) == "12"

        await pilot.click("#number-3")

        assert str(pilot.app.viewport) == "123"

Both of them fail because app.value is always "" and app.viewport is always "0", even though the GUI gets updated correctly.

[davep]

Both of them fail because app.value is always "" and app.viewport is always "0", even though the GUI gets updated correctly.

At first glance this sort of makes sense, when running with the pilot. What is happening is that the call to click is generating fake mouse messages (MouseDown, MouseUp and Click) and then returning after a pause. Those messages are going to then eventually have to result in a ButtonClicked message, which in turn will result in on_button_pressed being invoked, which in turn will result in value being changed, which in turn will eventually result in the Static that shows the numbers rendering the updated value.

Point being: by the time you get to the first assert most of that work won't have taken place yet.

However, it's reasonable to assume that the pilot.click should come back once the work has been done, so we'll dive a bit deeper into this and see if we can make that work.

[davep]

Right, found the issue and it's not what we were initially thinking. Fix is about to get under way.

Thanks for raising this; it's a good spot!

[github-actions[bot]]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.

[davep]

Just to update, this fix is now available: https://github.com/Textualize/textual/releases/tag/v0.15.0

[MalayAgr]

Thanks!