test: refine http body limit coverage

src/infra/http-body.test.ts

@@ -19,6 +19,49 @@ async function waitForMicrotaskTurn(): Promise<void> {
   await new Promise<void>((resolve) => queueMicrotask(resolve));
 }
 
+async function expectReadPayloadTooLarge(params: {
+  chunks?: string[];
+  headers?: Record<string, string>;
+  maxBytes: number;
+}) {
+  const req = createMockRequest({
+    chunks: params.chunks,
+    headers: params.headers,
+    emitEnd: false,
+  });
+  await expect(readRequestBodyWithLimit(req, { maxBytes: params.maxBytes })).rejects.toMatchObject({
+    message: "PayloadTooLarge",
+  });
+  await waitForMicrotaskTurn();
+  expect(req.__unhandledDestroyError).toBeUndefined();
+}
+
+async function expectGuardPayloadTooLarge(params: {
+  chunks?: string[];
+  headers?: Record<string, string>;
+  maxBytes: number;
+  responseFormat?: "json" | "text";
+  responseText?: { PAYLOAD_TOO_LARGE?: string };
+}) {
+  const req = createMockRequest({
+    chunks: params.chunks,
+    headers: params.headers,
+    emitEnd: false,
+  });
+  const res = createMockServerResponse();
+  const guard = installRequestBodyLimitGuard(req, res, {
+    maxBytes: params.maxBytes,
+    ...(params.responseFormat ? { responseFormat: params.responseFormat } : {}),
+    ...(params.responseText ? { responseText: params.responseText } : {}),
+  });
+  await waitForMicrotaskTurn();
+  expect(guard.isTripped()).toBe(true);
+  expect(guard.code()).toBe("PAYLOAD_TOO_LARGE");
+  expect(res.statusCode).toBe(413);
+  expect(req.__unhandledDestroyError).toBeUndefined();
+  return { req, res, guard };
+}
+
 function createMockRequest(params: {
   chunks?: string[];
   headers?: Record<string, string>;
@@ -66,12 +109,19 @@ describe("http body limits", () => {
     await expect(readRequestBodyWithLimit(req, { maxBytes: 1024 })).resolves.toBe('{"ok":true}');
   });
 
-  it("rejects oversized body", async () => {
-    const req = createMockRequest({ chunks: ["x".repeat(512)] });
-    await expect(readRequestBodyWithLimit(req, { maxBytes: 64 })).rejects.toMatchObject({
-      message: "PayloadTooLarge",
-    });
-    expect(req.__unhandledDestroyError).toBeUndefined();
+  it.each([
+    {
+      name: "rejects oversized streamed body",
+      chunks: ["x".repeat(512)],
+      maxBytes: 64,
+    },
+    {
+      name: "declared oversized content-length does not emit unhandled error",
+      headers: { "content-length": "9999" },
+      maxBytes: 128,
+    },
+  ])("$name", async ({ chunks, headers, maxBytes }) => {
+    await expectReadPayloadTooLarge({ chunks, headers, maxBytes });
   });
 
   it("returns json parse error when body is invalid", async () => {
@@ -83,34 +133,49 @@ describe("http body limits", () => {
     }
   });
 
+  it("returns empty object for an empty body by default", async () => {
+    const req = createMockRequest({ chunks: ["   "] });
+    const result = await readJsonBodyWithLimit(req, { maxBytes: 1024 });
+    expect(result).toEqual({ ok: true, value: {} });
+  });
+
   it("returns payload-too-large for json body", async () => {
     const req = createMockRequest({ chunks: ["x".repeat(1024)] });
     const result = await readJsonBodyWithLimit(req, { maxBytes: 10 });
     expect(result).toEqual({ ok: false, code: "PAYLOAD_TOO_LARGE", error: "Payload too large" });
   });
 
-  it("guard rejects oversized declared content-length", () => {
-    const req = createMockRequest({
+  it.each([
+    {
+      name: "guard rejects oversized declared content-length",
       headers: { "content-length": "9999" },
-      emitEnd: false,
+      maxBytes: 128,
+      expectedBody: '{"error":"Payload too large"}',
+    },
+    {
+      name: "guard rejects streamed oversized body",
+      chunks: ["small", "x".repeat(256)],
+      maxBytes: 128,
+      responseFormat: "text" as const,
+      expectedBody: "Payload too large",
+    },
+    {
+      name: "guard uses custom response text for payload-too-large",
+      chunks: ["small", "x".repeat(256)],
+      maxBytes: 128,
+      responseFormat: "text" as const,
+      responseText: { PAYLOAD_TOO_LARGE: "Too much" },
+      expectedBody: "Too much",
+    },
+  ])("$name", async ({ chunks, headers, maxBytes, responseFormat, responseText, expectedBody }) => {
+    const { res } = await expectGuardPayloadTooLarge({
+      chunks,
+      headers,
+      maxBytes,
+      ...(responseFormat ? { responseFormat } : {}),
+      ...(responseText ? { responseText } : {}),
     });
-    const res = createMockServerResponse();
-    const guard = installRequestBodyLimitGuard(req, res, { maxBytes: 128 });
-    expect(guard.isTripped()).toBe(true);
-    expect(guard.code()).toBe("PAYLOAD_TOO_LARGE");
-    expect(res.statusCode).toBe(413);
-  });
-
-  it("guard rejects streamed oversized body", async () => {
-    const req = createMockRequest({ chunks: ["small", "x".repeat(256)], emitEnd: false });
-    const res = createMockServerResponse();
-    const guard = installRequestBodyLimitGuard(req, res, { maxBytes: 128, responseFormat: "text" });
-    await waitForMicrotaskTurn();
-    expect(guard.isTripped()).toBe(true);
-    expect(guard.code()).toBe("PAYLOAD_TOO_LARGE");
-    expect(res.statusCode).toBe(413);
-    expect(res.body).toBe("Payload too large");
-    expect(req.__unhandledDestroyError).toBeUndefined();
+    expect(res.body).toBe(expectedBody);
   });
 
   it("timeout surfaces typed error when timeoutMs is clamped", async () => {
@@ -123,29 +188,20 @@ describe("http body limits", () => {
   });
 
   it("guard clamps invalid maxBytes to one byte", async () => {
-    const req = createMockRequest({ chunks: ["ab"], emitEnd: false });
-    const res = createMockServerResponse();
-    const guard = installRequestBodyLimitGuard(req, res, {
+    const { res } = await expectGuardPayloadTooLarge({
+      chunks: ["ab"],
       maxBytes: Number.NaN,
       responseFormat: "text",
     });
-    await waitForMicrotaskTurn();
-    expect(guard.isTripped()).toBe(true);
-    expect(guard.code()).toBe("PAYLOAD_TOO_LARGE");
-    expect(res.statusCode).toBe(413);
-    expect(req.__unhandledDestroyError).toBeUndefined();
+    expect(res.body).toBe("Payload too large");
   });
 
-  it("declared oversized content-length does not emit unhandled error", async () => {
-    const req = createMockRequest({
-      headers: { "content-length": "9999" },
-      emitEnd: false,
-    });
-    await expect(readRequestBodyWithLimit(req, { maxBytes: 128 })).rejects.toMatchObject({
-      message: "PayloadTooLarge",
-    });
-    // Wait a tick for any async destroy(err) emission.
-    await waitForMicrotaskTurn();
-    expect(req.__unhandledDestroyError).toBeUndefined();
+  it("surfaces connection-closed as a typed limit error", async () => {
+    const req = createMockRequest({ emitEnd: false });
+    const promise = readRequestBodyWithLimit(req, { maxBytes: 128 });
+    queueMicrotask(() => req.emit("close"));
+    await expect(promise).rejects.toSatisfy((error: unknown) =>
+      isRequestBodyLimitError(error, "CONNECTION_CLOSED"),
+    );
   });
 });