feat(FN-4218): complete Step 1 — define experiment session types

Fusion-Task-Id: FN-4218
Fusion-Task-Lineage: 0b50d7f4-5001-4eb6-9633-7b24b00097fd

packages/core/src/__tests__/experiment-session-types.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it } from "vitest";
+import {
+  EXPERIMENT_METRIC_DIRECTIONS,
+  EXPERIMENT_RECORD_TYPES,
+  EXPERIMENT_RUN_OUTCOMES,
+  EXPERIMENT_SESSION_STATUSES,
+  isConfigRecord,
+  isFinalizeRecord,
+  isHookRecord,
+  isRunRecord,
+  type ExperimentSessionRecord,
+} from "../experiment-session-types.js";
+
+describe("experiment-session-types", () => {
+  it("defines constants with expected members and order", () => {
+    expect(EXPERIMENT_SESSION_STATUSES).toEqual(["active", "finalizing", "finalized", "archived"]);
+    expect(EXPERIMENT_METRIC_DIRECTIONS).toEqual(["maximize", "minimize"]);
+    expect(EXPERIMENT_RECORD_TYPES).toEqual(["config", "run", "hook", "finalize"]);
+    expect(EXPERIMENT_RUN_OUTCOMES).toEqual(["keep", "discard", "checks_failed", "errored", "pending"]);
+  });
+
+  it("narrowing helpers identify record payload types", () => {
+    const records: ExperimentSessionRecord[] = [
+      {
+        id: "EXPR-1",
+        sessionId: "EXP-1",
+        segment: 1,
+        seq: 1,
+        type: "config",
+        payload: { metric: { name: "throughput", direction: "maximize" } },
+        createdAt: new Date().toISOString(),
+      },
+      {
+        id: "EXPR-2",
+        sessionId: "EXP-1",
+        segment: 1,
+        seq: 2,
+        type: "run",
+        payload: { primaryMetric: 123, secondaryMetrics: [], status: "keep" },
+        createdAt: new Date().toISOString(),
+      },
+      {
+        id: "EXPR-3",
+        sessionId: "EXP-1",
+        segment: 1,
+        seq: 3,
+        type: "hook",
+        payload: { hook: "before", exitCode: 0 },
+        createdAt: new Date().toISOString(),
+      },
+      {
+        id: "EXPR-4",
+        sessionId: "EXP-1",
+        segment: 1,
+        seq: 4,
+        type: "finalize",
+        payload: { keptRunIds: ["EXPR-2"], discardedRunIds: [] },
+        createdAt: new Date().toISOString(),
+      },
+    ];
+
+    const [config, run, hook, finalize] = records;
+    expect(isConfigRecord(config)).toBe(true);
+    expect(isRunRecord(config)).toBe(false);
+    expect(isRunRecord(run)).toBe(true);
+    expect(run.payload.primaryMetric).toBe(123);
+    expect(isHookRecord(hook)).toBe(true);
+    expect(hook.payload.hook).toBe("before");
+    expect(isFinalizeRecord(finalize)).toBe(true);
+    expect(finalize.payload.keptRunIds).toEqual(["EXPR-2"]);
+  });
+});