Textual Test Patterns

Testing recipes for specific Textual scenarios. Each pattern shows complete, working test code.

Pattern Index

Scenario	Pattern
Keyboard shortcuts	Test Keyboard Shortcuts
Screen transitions	Test Screen Transitions
Focus management	Test Focus Management
Reactive attributes	Test Reactive Attributes
Custom messages	Test Custom Messages
CSS styling	Test CSS Styling
Data tables	Test Data Tables
Scrolling	Test Scrolling
Input validation	Test Input Validation
Error states	Test Error States
Loading states	Test Loading States
Background workers	Test Background Workers

Test Keyboard Shortcuts

async def test_keyboard_shortcuts():
    """Test keyboard binding triggers action."""
    class MyApp(App):
        BINDINGS = [("ctrl+s", "save", "Save")]
        saved = False

        def action_save(self) -> None:
            self.saved = True

    async with MyApp().run_test() as pilot:
        await pilot.press("ctrl+s")
        await pilot.pause()
        assert pilot.app.saved is True

Test Screen Transitions

from textual.screen import Screen

class MainScreen(Screen):
    pass

class SettingsScreen(Screen):
    pass

async def test_screen_navigation():
    """Test navigating between screens."""
    class MyApp(App):
        SCREENS = {"settings": SettingsScreen}

        def compose(self):
            yield Static("Main")

        def key_s(self):
            self.push_screen("settings")

    async with MyApp().run_test() as pilot:
        # Start on default screen
        assert not isinstance(pilot.app.screen, SettingsScreen)

        # Navigate to settings
        await pilot.press("s")
        await pilot.pause()
        assert isinstance(pilot.app.screen, SettingsScreen)

        # Navigate back
        await pilot.press("escape")
        await pilot.pause()
        assert not isinstance(pilot.app.screen, SettingsScreen)

Test Focus Management

from textual.widgets import Input

async def test_focus_order():
    """Test Tab moves focus through widgets."""
    class MyApp(App):
        def compose(self):
            yield Input(id="name")
            yield Input(id="email")
            yield Input(id="phone")

    async with MyApp().run_test() as pilot:
        name = pilot.app.query_one("#name", Input)
        email = pilot.app.query_one("#email", Input)

        # First input focused by default
        assert name.has_focus

        # Tab to next
        await pilot.press("tab")
        await pilot.pause()
        assert email.has_focus
        assert not name.has_focus

        # Shift+Tab back
        await pilot.press("shift+tab")
        await pilot.pause()
        assert name.has_focus

Test Reactive Attributes

from textual.reactive import reactive
from textual.widgets import Static

class StatusWidget(Static):
    status: reactive[str] = reactive("idle")

    def watch_status(self, new_status: str) -> None:
        self.add_class(f"status-{new_status}")
        self.remove_class(f"status-{self._previous_status}")
        self._previous_status = new_status

    def __init__(self):
        super().__init__()
        self._previous_status = "idle"

async def test_reactive_attribute():
    """Test reactive attribute triggers watcher."""
    class TestApp(App):
        def compose(self):
            yield StatusWidget(id="status")

    async with TestApp().run_test() as pilot:
        widget = pilot.app.query_one("#status", StatusWidget)

        assert widget.status == "idle"
        assert widget.has_class("status-idle")

        widget.status = "loading"
        await pilot.pause()

        assert widget.has_class("status-loading")
        assert not widget.has_class("status-idle")

Test Custom Messages

from textual.message import Message

class ItemSelected(Message):
    def __init__(self, item_id: str) -> None:
        super().__init__()
        self.item_id = item_id

async def test_custom_message():
    """Test custom message is received by handler."""
    class MyApp(App):
        selected_items: list[str] = []

        def compose(self):
            yield Static("Item", id="item")

        def on_item_selected(self, message: ItemSelected) -> None:
            self.selected_items.append(message.item_id)

    async with MyApp().run_test() as pilot:
        # Post message
        pilot.app.post_message(ItemSelected("item-1"))
        await pilot.pause()

        assert pilot.app.selected_items == ["item-1"]

        # Post another
        pilot.app.post_message(ItemSelected("item-2"))
        await pilot.pause()

        assert pilot.app.selected_items == ["item-1", "item-2"]

Test CSS Styling

from textual.color import Color

async def test_css_class_application():
    """Test CSS class changes styling."""
    class MyApp(App):
        CSS = """
        .error { background: red; }
        .success { background: green; }
        """

        def compose(self):
            yield Static("Status", id="status")

    async with MyApp().run_test() as pilot:
        status = pilot.app.query_one("#status")

        # Add error class
        status.add_class("error")
        await pilot.pause()
        assert status.has_class("error")

        # Switch to success
        status.remove_class("error")
        status.add_class("success")
        await pilot.pause()
        assert status.has_class("success")
        assert not status.has_class("error")

Test Data Tables

from textual.widgets import DataTable

async def test_data_table():
    """Test data table row selection."""
    class MyApp(App):
        def compose(self):
            yield DataTable(id="table")

        def on_mount(self):
            table = self.query_one("#table", DataTable)
            table.add_columns("Name", "Value")
            table.add_rows([
                ("Alice", "100"),
                ("Bob", "200"),
                ("Carol", "300"),
            ])

    async with MyApp().run_test() as pilot:
        table = pilot.app.query_one("#table", DataTable)

        assert table.row_count == 3

        # Navigate and select
        await pilot.click(DataTable)
        await pilot.press("down", "down")
        await pilot.pause()

        assert table.cursor_row == 2

Test Scrolling

from textual.containers import ScrollableContainer

async def test_scrolling():
    """Test scroll position changes."""
    class MyApp(App):
        def compose(self):
            with ScrollableContainer(id="container"):
                for i in range(100):
                    yield Static(f"Line {i}")

    async with MyApp().run_test(size=(80, 10)) as pilot:
        container = pilot.app.query_one("#container", ScrollableContainer)

        # Start at top
        assert container.scroll_y == 0

        # Scroll down
        await pilot.press("pagedown")
        await pilot.pause()
        assert container.scroll_y > 0

        # Scroll to end
        await pilot.press("end")
        await pilot.pause()
        assert container.scroll_y == container.max_scroll_y

Test Input Validation

from textual.widgets import Input
from textual.validation import Validator, ValidationResult

class EmailValidator(Validator):
    def validate(self, value: str) -> ValidationResult:
        if "@" in value and "." in value.split("@")[-1]:
            return self.success()
        return self.failure("Invalid email")

async def test_input_validation():
    """Test input field validates correctly."""
    class MyApp(App):
        def compose(self):
            yield Input(id="email", validators=[EmailValidator()])

    async with MyApp().run_test() as pilot:
        input_widget = pilot.app.query_one("#email", Input)

        # Invalid input
        await pilot.click(Input)
        await pilot.press(*"invalid")
        await pilot.pause()
        assert not input_widget.is_valid

        # Clear and enter valid
        input_widget.value = ""
        await pilot.press(*"user@example.com")
        await pilot.pause()
        assert input_widget.is_valid

Test Error States

async def test_error_display():
    """Test error message shows and dismisses."""
    class MyApp(App):
        def compose(self):
            yield Static("", id="error", classes="hidden")

        def show_error(self, msg: str):
            error = self.query_one("#error")
            error.update(msg)
            error.remove_class("hidden")

        def dismiss_error(self):
            self.query_one("#error").add_class("hidden")

    async with MyApp().run_test() as pilot:
        error = pilot.app.query_one("#error")

        # Initially hidden
        assert error.has_class("hidden")

        # Show error
        pilot.app.show_error("Something went wrong")
        await pilot.pause()
        assert not error.has_class("hidden")
        assert "Something went wrong" in error.renderable

        # Dismiss
        pilot.app.dismiss_error()
        await pilot.pause()
        assert error.has_class("hidden")

Test Loading States

async def test_loading_indicator():
    """Test loading state shows during async work."""
    class MyApp(App):
        loading = False

        def compose(self):
            yield Static("Ready", id="status")

        async def load_data(self):
            self.loading = True
            self.query_one("#status").update("Loading...")
            # Simulate async work
            await asyncio.sleep(0.1)
            self.loading = False
            self.query_one("#status").update("Loaded")

    async with MyApp().run_test() as pilot:
        status = pilot.app.query_one("#status")

        # Before loading
        assert "Ready" in status.renderable

        # Start loading (don't await)
        task = asyncio.create_task(pilot.app.load_data())
        await pilot.pause(0.05)

        # During loading
        assert pilot.app.loading is True

        # After loading
        await task
        await pilot.pause()
        assert pilot.app.loading is False
        assert "Loaded" in status.renderable

Test Background Workers

async def test_worker_completion():
    """Test background worker completes and updates state."""
    class MyApp(App):
        data = None

        def compose(self):
            yield Static("", id="result")

        @work
        async def fetch_data(self):
            await asyncio.sleep(0.1)
            self.data = {"items": [1, 2, 3]}
            self.query_one("#result").update(str(self.data))

    async with MyApp().run_test() as pilot:
        # Trigger worker
        pilot.app.fetch_data()

        # Wait for completion
        await pilot.app.workers.wait_for_complete()

        # Verify result
        assert pilot.app.data == {"items": [1, 2, 3]}

Common Pitfalls

Issue	Fix
Assertion before update	Add await pilot.pause() after interactions
Worker not complete	Use await pilot.app.workers.wait_for_complete()
Animation interference	Use await pilot.wait_for_animation()
Race condition	Increase pause duration or use explicit waits

See Also

• textual-testing - Core Pilot API reference
• textual-test-fixtures - Fixture patterns
• textual-snapshot-testing - Visual regression