feat: port release-v2 experience improvements from #6582 (audited subset) (#6609)

packages/integrations/src/base/response-contract.spec.ts

@@ -0,0 +1,43 @@
+import { describe, expect, test } from "vitest";
+import { z } from "zod/v4";
+
+import { simulateResponseContractAsync } from "./response-contract";
+
+const parser = async (response: { json: () => Promise<unknown> }) =>
+  z.object({ count: z.number() }).parse(await response.json());
+
+describe("simulateResponseContractAsync", () => {
+  test("runs valid, mapped, and rejected payload fixtures", async () => {
+    const results = await simulateResponseContractAsync(
+      parser,
+      [
+        { name: "valid response", payload: { count: 2 }, expected: { total: 2 } },
+        { name: "invalid response", payload: { count: "two" }, rejects: true },
+      ],
+      (value) => ({ total: value.count }),
+    );
+
+    expect(results).toEqual([
+      { name: "valid response", passed: true, message: undefined },
+      { name: "invalid response", passed: true, message: undefined },
+    ]);
+  });
+
+  test("treats a fixture without expected or rejects as a successful parse assertion", async () => {
+    const results = await simulateResponseContractAsync(parser, [{ name: "parses only", payload: { count: 5 } }]);
+
+    expect(results).toEqual([{ name: "parses only", passed: true, message: undefined }]);
+  });
+
+  test("reports actionable mismatches without throwing away later fixtures", async () => {
+    const results = await simulateResponseContractAsync(parser, [
+      { name: "wrong output", payload: { count: 2 }, expected: { count: 3 } },
+      { name: "unexpected success", payload: { count: 4 }, rejects: true },
+    ]);
+
+    expect(results).toEqual([
+      { name: "wrong output", passed: false, message: "Parsed output did not match expected." },
+      { name: "unexpected success", passed: false, message: "Expected parser rejection, but parsing succeeded." },
+    ]);
+  });
+});