Add sub-component support via self-referential device hierarchy

tests/test_acceptance.py

@@ -885,3 +885,99 @@ def test_device_charge_all_no_installed(seeded_client):
     )
     assert resp.status_code == 200
     assert b"No installed batteries" in resp.data
+
+
+# ------------------------------------------------------------------ #
+# Sub-components (self-referential device hierarchy)
+# ------------------------------------------------------------------ #
+
+def _setup_rc_car(client):
+    """Create RC Car Set with Remote and Car sub-components and 6 AA batteries."""
+    client.post("/device/add", data={"name": "RC Car Set", "battery_slots": "6", "battery_size": "AA"})
+    # id=1 above; add sub-components with parent_id=1
+    client.post("/device/add", data={"name": "Remote", "battery_slots": "2",
+                                     "battery_size": "AA", "parent_id": "1"})
+    client.post("/device/add", data={"name": "Car", "battery_slots": "4",
+                                     "battery_size": "AA", "parent_id": "1"})
+    for i in range(1, 7):
+        client.post("/battery/add", data={"brand": "Eneloop", "label": f"E{i:03d}", "size": "AA"})
+
+
+def test_add_subcomponent(client):
+    _setup_rc_car(client)
+    # Parent detail shows sub-components
+    resp = client.get("/device/1")
+    assert resp.status_code == 200
+    assert b"Remote" in resp.data
+    assert b"Car" in resp.data
+    # Child detail shows breadcrumb back to parent
+    resp = client.get("/device/2")
+    assert resp.status_code == 200
+    assert b"RC Car Set" in resp.data
+    assert b"Remote" in resp.data
+
+
+def test_subcomponent_prevents_deep_nesting(client):
+    _setup_rc_car(client)
+    # id=2 is "Remote", which already has parent_id=1
+    resp = client.post("/device/add", data={"name": "Button", "battery_slots": "1",
+                                            "battery_size": "AA", "parent_id": "2"})
+    assert resp.status_code == 400
+    assert b"one level" in resp.data.lower() or b"nest" in resp.data.lower()
+
+
+def test_subcomponent_install_batteries(client):
+    _setup_rc_car(client)
+    # Install 2 batteries into Remote (device id=2)
+    resp = client.post("/device/2/install-one", data={"battery_id": "1"}, follow_redirects=True)
+    assert resp.status_code == 200
+    resp = client.post("/device/2/install-one", data={"battery_id": "2"}, follow_redirects=True)
+    assert resp.status_code == 200
+    # Remote is now full (2/2); a third battery should be blocked
+    resp = client.post("/device/2/install-one", data={"battery_id": "3"}, follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"full" in resp.data.lower()
+
+
+def test_dashboard_shows_parent_slash_child(client):
+    _setup_rc_car(client)
+    client.post("/device/2/install-one", data={"battery_id": "1"})
+    resp = client.get("/", follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"RC Car Set" in resp.data
+    assert b"Remote" in resp.data
+
+
+def test_delete_parent_promotes_children(client):
+    _setup_rc_car(client)
+    client.post("/device/1/delete", follow_redirects=True)
+    # Child devices still exist
+    resp = client.get("/device/2")
+    assert resp.status_code == 200
+    resp = client.get("/device/3")
+    assert resp.status_code == 200
+
+
+def test_device_without_parent_unchanged(client):
+    client.post("/device/add", data={"name": "Torch", "battery_slots": "2", "battery_size": "AA"})
+    client.post("/battery/add", data={"brand": "Eneloop", "count": "1"})
+    resp = client.post("/device/1/install-one", data={"battery_id": "1"}, follow_redirects=True)
+    assert resp.status_code == 200
+    assert b"1 / 2" in resp.data
+
+
+def test_subcomponent_ha_entity_id(client):
+    client.post("/device/add", data={"name": "Hub", "battery_slots": "1", "battery_size": "AA"})
+    resp = client.post(
+        "/device/add",
+        data={"name": "Sensor A", "battery_slots": "1", "battery_size": "AA",
+              "parent_id": "1", "ha_entity_id": "sensor.sensor_a_battery"},
+        follow_redirects=True,
+    )
+    # Redirects to parent detail on success
+    assert resp.status_code == 200
+    assert b"Sensor A" in resp.data
+    # Child detail shows parent breadcrumb
+    resp = client.get("/device/2")
+    assert resp.status_code == 200
+    assert b"Hub" in resp.data