Run KVM switch in background and target DDM by monitor model

tests/test_app.py

@@ -167,3 +167,75 @@ def test_polling_switches_when_trigger_matches_device_role(monkeypatch: pytest.M
     assert status["samsung_session_attempted"] is True
     assert status["samsung_session_successful"] is True
     assert status["last_switch_result"] == "switched"
+
+
+def test_polling_switches_with_monitor_targeting_when_slot_is_unavailable(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setenv(DEVICE_ROLE_ENV_VAR, "tower")
+    service_module = _require_module("app.service")
+    hardware_module = _require_module("app.hardware")
+    ddm_module = _require_module("app.ddm")
+
+    KvmSwitcherService = getattr(service_module, "KvmSwitcherService", None)
+    HardwareScan = getattr(hardware_module, "HardwareScan", None)
+    DDMCommandResult = getattr(ddm_module, "DDMCommandResult", None)
+    if KvmSwitcherService is None or HardwareScan is None or DDMCommandResult is None:
+        pytest.skip("Service backend interfaces are not available yet.")
+
+    class FakeMonitorBackend:
+        def __init__(self) -> None:
+            self.call_count = 0
+
+        def scan(self):
+            self.call_count += 1
+            if self.call_count == 1:
+                return HardwareScan(
+                    samsung_present=True,
+                    trigger_input_code=15,
+                    alienware_detected=True,
+                    alienware_input_code=19,
+                    errors=[],
+                )
+            return HardwareScan(
+                samsung_present=True,
+                trigger_input_code=15,
+                alienware_detected=True,
+                alienware_input_code=15,
+                errors=[],
+            )
+
+    class FakeDDMBackend:
+        def __init__(self) -> None:
+            self.calls: list[tuple[int, str]] = []
+
+        def is_available(self) -> bool:
+            return True
+
+        def supports_monitor_targeting(self) -> bool:
+            return True
+
+        def resolve_alienware_slot(self, force: bool = False) -> int | None:
+            return None
+
+        def invalidate_slot(self) -> None:
+            return None
+
+        def switch_to_port(self, slot: int, port_name: str):
+            self.calls.append((slot, port_name))
+            return DDMCommandResult(True, "ok")
+
+    config_path = Path(tempfile.mkdtemp()) / "config.json"
+    backend = FakeDDMBackend()
+    service = KvmSwitcherService(
+        config_store=ConfigStore(config_path),
+        monitor_backend=FakeMonitorBackend(),
+        ddm_backend=backend,
+        poll_interval_seconds=0.01,
+        retry_wait_seconds=0.0,
+    )
+    status = service.save_settings(device_role="tower", device_port="DP1")
+    assert status["ddm_ready"] is True
+    assert status["ddm_slot"] is None
+    assert status["last_switch_result"] == "switched"
+    assert backend.calls == [(0, "DP1")]