refactor: add equipment registry

backend/tests/unit/test_equipment_registry.py

@@ -0,0 +1,30 @@
+from core.basic.equipment import get_equipment
+from core.basic.equipment_registry import EquipmentRegistry
+
+
+def test_get_equipment_returns_cached_default_version():
+    first = get_equipment('0')
+    second = get_equipment('0')
+
+    assert first is second
+    assert first.version == '0'
+
+
+def test_get_equipment_falls_back_to_default_version():
+    equipment = get_equipment('missing-version')
+
+    assert equipment.version == '0'
+
+
+def test_equipment_registry_caches_by_version():
+    calls = []
+
+    class Equipment:
+        def __init__(self, version):
+            calls.append(version)
+            self.version = version
+
+    registry = EquipmentRegistry(Equipment)
+
+    assert registry.get('0') is registry.get('0')
+    assert calls == ['0']