test(FN-4459): complete Step 2 — add experiment session accessor tests

Fusion-Task-Id: FN-4459
Fusion-Task-Lineage: 3448a074-fa1c-45d6-8bb9-cc5922cee7f6

packages/core/src/__tests__/store.experiment-session-accessor.test.ts

@@ -0,0 +1,58 @@
+import { beforeEach, afterEach, describe, expect, it } from "vitest";
+import { ExperimentSessionStore } from "../experiment-session-store.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+describe("TaskStore getExperimentSessionStore", () => {
+  const harness = createTaskStoreTestHarness();
+
+  beforeEach(harness.beforeEach);
+  afterEach(harness.afterEach);
+
+  it("returns an ExperimentSessionStore instance", () => {
+    const accessorStore = harness.store().getExperimentSessionStore();
+    expect(accessorStore).toBeInstanceOf(ExperimentSessionStore);
+  });
+
+  it("returns the same cached instance across calls", () => {
+    const store = harness.store();
+    const first = store.getExperimentSessionStore();
+    const second = store.getExperimentSessionStore();
+    expect(second).toBe(first);
+  });
+
+  it("uses the same project database backing storage", () => {
+    const taskStore = harness.store();
+    const accessorStore = taskStore.getExperimentSessionStore();
+
+    accessorStore.createSession({
+      name: "session-from-accessor",
+      metric: { name: "latency", direction: "minimize" },
+    });
+
+    const directStore = new ExperimentSessionStore(taskStore.getDatabase());
+    const sessions = directStore.listSessions();
+
+    expect(sessions).toHaveLength(1);
+    expect(sessions[0]?.name).toBe("session-from-accessor");
+  });
+
+  it("does not initialize research store when experiment accessor is called", () => {
+    const taskStore = harness.store() as unknown as {
+      getExperimentSessionStore: () => ExperimentSessionStore;
+      getResearchStore: () => unknown;
+      experimentSessionStore: ExperimentSessionStore | null;
+      researchStore: unknown;
+    };
+
+    expect(taskStore.researchStore).toBeNull();
+    expect(taskStore.experimentSessionStore).toBeNull();
+
+    taskStore.getExperimentSessionStore();
+
+    expect(taskStore.experimentSessionStore).toBeInstanceOf(ExperimentSessionStore);
+    expect(taskStore.researchStore).toBeNull();
+
+    const research = taskStore.getResearchStore();
+    expect(research).toBeTruthy();
+  });
+});