Add unit test for NPC actor registry

tests/unit/npc-actor-registry.test.ts

@@ -0,0 +1,70 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  createEmptyProjectDocument,
+  createEmptyProjectScene
+} from "../../src/document/scene-document";
+import {
+  createNpcEntity,
+  createPointLightEntity
+} from "../../src/entities/entity-instances";
+import { listNpcActorUsages } from "../../src/entities/npc-actor-registry";
+
+describe("listNpcActorUsages", () => {
+  it("finds matching NPC actor ids across project scenes", () => {
+    const villageNpc = createNpcEntity({
+      id: "entity-npc-village-guide",
+      name: "Village Guide",
+      actorId: "actor-town-guide"
+    });
+    const plazaNpc = createNpcEntity({
+      id: "entity-npc-plaza-guide",
+      name: "Plaza Guide",
+      actorId: "actor-town-guide"
+    });
+    const otherNpc = createNpcEntity({
+      id: "entity-npc-baker",
+      actorId: "actor-town-baker"
+    });
+    const project = createEmptyProjectDocument({
+      sceneId: "scene-village",
+      sceneName: "Village"
+    });
+
+    project.scenes["scene-village"].entities = {
+      [villageNpc.id]: villageNpc,
+      [otherNpc.id]: otherNpc,
+      "entity-point-light": createPointLightEntity({
+        id: "entity-point-light"
+      })
+    };
+    project.scenes["scene-plaza"] = createEmptyProjectScene({
+      id: "scene-plaza",
+      name: "Plaza"
+    });
+    project.scenes["scene-plaza"].entities = {
+      [plazaNpc.id]: plazaNpc
+    };
+
+    expect(listNpcActorUsages(project, "actor-town-guide")).toEqual([
+      {
+        actorId: "actor-town-guide",
+        sceneId: "scene-plaza",
+        sceneName: "Plaza",
+        entityId: "entity-npc-plaza-guide",
+        entityName: "Plaza Guide"
+      },
+      {
+        actorId: "actor-town-guide",
+        sceneId: "scene-village",
+        sceneName: "Village",
+        entityId: "entity-npc-village-guide",
+        entityName: "Village Guide"
+      }
+    ]);
+  });
+
+  it("returns no usages for a blank actor id", () => {
+    expect(listNpcActorUsages(createEmptyProjectDocument(), "   ")).toEqual([]);
+  });
+});