test: reorganize core suite into explicit domain files

tests/ui/test_ui_filter_screen_behavior.py

@@ -0,0 +1,62 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Callable, cast
+
+from auditui.ui import FilterScreen
+from textual.widgets import Input
+
+
+@dataclass(slots=True)
+class DummyEvent:
+    """Minimal event object carrying an input value for tests."""
+
+    value: str
+
+
+@dataclass(slots=True)
+class FakeTimer:
+    """Timer substitute recording whether stop() was called."""
+
+    callback: Callable[[], None]
+    stopped: bool = False
+
+    def stop(self) -> None:
+        """Mark timer as stopped."""
+        self.stopped = True
+
+
+def test_filter_debounce_uses_latest_value(monkeypatch) -> None:
+    """Ensure debounce cancels previous timer and emits latest input value."""
+    seen: list[str] = []
+    timers: list[FakeTimer] = []
+
+    def on_change(value: str) -> None:
+        """Capture emitted filter values."""
+        seen.append(value)
+
+    screen = FilterScreen(on_change=on_change, debounce_seconds=0.2)
+
+    def fake_set_timer(_delay: float, callback: Callable[[], None]) -> FakeTimer:
+        """Record timer callbacks instead of scheduling real timers."""
+        timer = FakeTimer(callback)
+        timers.append(timer)
+        return timer
+
+    monkeypatch.setattr(screen, "set_timer", fake_set_timer)
+    screen.on_input_changed(cast(Input.Changed, DummyEvent("a")))
+    screen.on_input_changed(cast(Input.Changed, DummyEvent("ab")))
+    assert len(timers) == 2
+    assert timers[0].stopped is True
+    assert timers[1].stopped is False
+    timers[1].callback()
+    assert seen == ["ab"]
+
+
+def test_on_unmount_stops_pending_timer() -> None:
+    """Ensure screen unmount stops pending debounce timer when present."""
+    screen = FilterScreen(on_change=lambda _value: None)
+    timer = FakeTimer(lambda: None)
+    screen._debounce_timer = timer
+    screen.on_unmount()
+    assert timer.stopped is True