diff --git a/CHANGELOG.md b/CHANGELOG.md
index 02f3e4f..ba451ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.15.0 (2022/12/01)
+
+- Breaking change: createHttpError & createJSONHttpError params are no longer optional
+- Test with Undici fetch
+
 ## 0.14.2 (2022/12/01)
 
 - Update npm packages
diff --git a/README.md b/README.md
index 90c3d98..a2908fb 100644
--- a/README.md
+++ b/README.md
@@ -130,8 +130,8 @@ Check [examples/web](examples/web)
 - `createResponsePromise(body?:` [`BodyInit`](https://fetch.spec.whatwg.org/#bodyinit)`, init?:` [`ResponseInit`](https://fetch.spec.whatwg.org/#responseinit)`): ResponsePromiseWithBodyMethods`
 - `createJSONResponsePromise(body: object, init?: ResponseInit): ResponsePromiseWithBodyMethods`
 
-- `createHttpError(body?: BodyInit, status = 0, statusText?: string): HttpError`
-- `createJSONHttpError(body: object, status = 0, statusText?: string): HttpError`
+- `createHttpError(body: BodyInit, status: number, statusText?: string): HttpError`
+- `createJSONHttpError(body: object, status: number, statusText?: string): HttpError`
 
 ### HttpStatus
 
diff --git a/jest.setup.ts b/jest.setup.ts
index ef050cc..0e446cf 100644
--- a/jest.setup.ts
+++ b/jest.setup.ts
@@ -10,17 +10,27 @@ switch (fetchPolyfill) {
   case 'whatwg-fetch': {
     const whatwgFetch = require('whatwg-fetch');
     globalThis.fetch = whatwgFetch.fetch;
-    // Tests are very slow with whatwg-fetch (150s) vs node-fetch (2s)
-    jest.setTimeout(10_000);
+    globalThis.Request = whatwgFetch.Request;
+    globalThis.Response = whatwgFetch.Response;
+    globalThis.Headers = whatwgFetch.Headers;
     break;
   }
   case 'node-fetch': {
     const nodeFetch = require('node-fetch');
     globalThis.fetch = nodeFetch.default;
+    globalThis.Request = nodeFetch.Request;
     globalThis.Response = nodeFetch.Response;
     globalThis.Headers = nodeFetch.Headers;
     break;
   }
+  case 'undici': {
+    const undici = require('undici');
+    globalThis.fetch = undici.fetch;
+    globalThis.Request = undici.Request;
+    globalThis.Response = undici.Response;
+    globalThis.Headers = undici.Headers;
+    break;
+  }
   default: {
     assert(false, `Invalid fetch polyfill: '${fetchPolyfill}'`);
   }
diff --git a/package-lock.json b/package-lock.json
index 8eeb29f..1123456 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -40,6 +40,7 @@
         "tslib": "^2.4.1",
         "typescript": "^4.9.3",
         "ua-parser-js": "^1.0.32",
+        "undici": "^5.13.0",
         "whatwg-fetch": "^3.6.2"
       }
     },
@@ -3747,6 +3748,18 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/busboy": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/busboy/-/busboy-1.6.0.tgz",
+      "integrity": "sha512-8SFQbg/0hQ9xy3UNTB0YEnsNBbWfhf7RtnzpL7TkBiTBRfrQ9Fxcnz7VJsleJpyp6rVLvXiuORqjlHi5q+PYuA==",
+      "dev": true,
+      "dependencies": {
+        "streamsearch": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=10.16.0"
+      }
+    },
     "node_modules/call-bind": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/call-bind/-/call-bind-1.0.2.tgz",
@@ -9333,6 +9346,15 @@
         "node": ">=8"
       }
     },
+    "node_modules/streamsearch": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/streamsearch/-/streamsearch-1.1.0.tgz",
+      "integrity": "sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==",
+      "dev": true,
+      "engines": {
+        "node": ">=10.0.0"
+      }
+    },
     "node_modules/string-length": {
       "version": "4.0.2",
       "resolved": "https://registry.npmjs.org/string-length/-/string-length-4.0.2.tgz",
@@ -9704,6 +9726,18 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/undici": {
+      "version": "5.13.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-5.13.0.tgz",
+      "integrity": "sha512-UDZKtwb2k7KRsK4SdXWG7ErXiL7yTGgLWvk2AXO1JMjgjh404nFo6tWSCM2xMpJwMPx3J8i/vfqEh1zOqvj82Q==",
+      "dev": true,
+      "dependencies": {
+        "busboy": "^1.6.0"
+      },
+      "engines": {
+        "node": ">=12.18"
+      }
+    },
     "node_modules/unicode-canonical-property-names-ecmascript": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-2.0.0.tgz",
@@ -12771,6 +12805,15 @@
       "integrity": "sha512-zhaCDicdLuWN5UbN5IMnFqNMhNfo919sH85y2/ea+5Yg9TsTkeZxpL+JLbp6cgYFS4sRLp3YV4S6yDuqVWHYOw==",
       "dev": true
     },
+    "busboy": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/busboy/-/busboy-1.6.0.tgz",
+      "integrity": "sha512-8SFQbg/0hQ9xy3UNTB0YEnsNBbWfhf7RtnzpL7TkBiTBRfrQ9Fxcnz7VJsleJpyp6rVLvXiuORqjlHi5q+PYuA==",
+      "dev": true,
+      "requires": {
+        "streamsearch": "^1.1.0"
+      }
+    },
     "call-bind": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/call-bind/-/call-bind-1.0.2.tgz",
@@ -16887,6 +16930,12 @@
         }
       }
     },
+    "streamsearch": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/streamsearch/-/streamsearch-1.1.0.tgz",
+      "integrity": "sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==",
+      "dev": true
+    },
     "string-length": {
       "version": "4.0.2",
       "resolved": "https://registry.npmjs.org/string-length/-/string-length-4.0.2.tgz",
@@ -17158,6 +17207,15 @@
         "which-boxed-primitive": "^1.0.2"
       }
     },
+    "undici": {
+      "version": "5.13.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-5.13.0.tgz",
+      "integrity": "sha512-UDZKtwb2k7KRsK4SdXWG7ErXiL7yTGgLWvk2AXO1JMjgjh404nFo6tWSCM2xMpJwMPx3J8i/vfqEh1zOqvj82Q==",
+      "dev": true,
+      "requires": {
+        "busboy": "^1.6.0"
+      }
+    },
     "unicode-canonical-property-names-ecmascript": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-2.0.0.tgz",
diff --git a/package.json b/package.json
index 70e2749..55baf32 100644
--- a/package.json
+++ b/package.json
@@ -37,6 +37,7 @@
     "test:node-fetch": "NODE_EXTRA_CA_CERTS=./src/createTestServer/createTestServer.cert FETCH=node-fetch jest --verbose",
     "test:coverage:node-fetch": "NODE_EXTRA_CA_CERTS=./src/createTestServer/createTestServer.cert FETCH=node-fetch jest --coverage",
     "test:whatwg-fetch": "NODE_EXTRA_CA_CERTS=./src/createTestServer/createTestServer.cert FETCH=whatwg-fetch jest --env=jsdom --verbose",
+    "test:undici": "NODE_EXTRA_CA_CERTS=./src/createTestServer/createTestServer.cert FETCH=undici jest --verbose",
     "test:coverage:whatwg-fetch": "NODE_EXTRA_CA_CERTS=./src/createTestServer/createTestServer.cert FETCH=whatwg-fetch jest --env=jsdom --coverage",
     "test:e2e": "playwright test",
     "test:e2e:debug": "playwright test --debug",
@@ -89,6 +90,7 @@
     "tslib": "^2.4.1",
     "typescript": "^4.9.3",
     "ua-parser-js": "^1.0.32",
+    "undici": "^5.13.0",
     "whatwg-fetch": "^3.6.2"
   }
 }
diff --git a/src/Http.test.ts b/src/Http.test.ts
index 888c7fc..ace1f26 100644
--- a/src/Http.test.ts
+++ b/src/Http.test.ts
@@ -2,7 +2,6 @@ import assert from 'node:assert';
 
 import { createTestServer } from './createTestServer/createTestServer';
 import { entriesToObject } from './utils/entriesToObject';
-import { isWhatwgFetch } from './utils/isWhatwgFetch';
 import { defaults, del, get, patch, patchJSON, post, postJSON, put, putJSON } from './Http';
 
 const path = '/';
@@ -480,7 +479,7 @@ describe('body methods', () => {
     const response = await get(url).blob();
     expect(response.size).toEqual(3);
     // FIXME https://github.com/jsdom/jsdom/issues/2555
-    if (!isWhatwgFetch) {
+    if (process.env.FETCH !== 'whatwg-fetch') {
       // eslint-disable-next-line jest/no-conditional-expect
       expect(await response.text()).toEqual('*/*');
     }
@@ -598,11 +597,24 @@ describe('body methods', () => {
   });
 
   // https://github.com/whatwg/fetch/issues/1147
-  // eslint-disable-next-line unicorn/consistent-function-scoping
-  const nodeFetchBodyAlreadyUsedError = (url: string) => `body used already for: ${url}`;
-  const whatwgFetchBodyAlreadyUsedError = 'Already read';
-  const bodyAlreadyUsedError = (url: string) =>
-    isWhatwgFetch ? whatwgFetchBodyAlreadyUsedError : nodeFetchBodyAlreadyUsedError(url);
+  let bodyAlreadyUsedError = '';
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      bodyAlreadyUsedError = 'body used already for: ';
+      break;
+    }
+    case 'whatwg-fetch': {
+      bodyAlreadyUsedError = 'Already read';
+      break;
+    }
+    case 'undici': {
+      bodyAlreadyUsedError = 'Body is unusable';
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
 
   test('multiple body calls using helpers', async () => {
     const server = createTestServer();
@@ -614,7 +626,7 @@ describe('body methods', () => {
 
     const response = get(url);
     expect(await response.json()).toEqual({ accept: 'application/json' });
-    await expect(response.text()).rejects.toThrow(bodyAlreadyUsedError(url));
+    await expect(response.text()).rejects.toThrow(bodyAlreadyUsedError);
 
     // FIXME await close() is too slow with Fastify 4.10.2
     server.close();
@@ -630,7 +642,7 @@ describe('body methods', () => {
 
     const response = await get(url);
     expect(await response.json()).toEqual({ accept: '*/*' });
-    await expect(response.text()).rejects.toThrow(bodyAlreadyUsedError(url));
+    await expect(response.text()).rejects.toThrow(bodyAlreadyUsedError);
 
     // FIXME await close() is too slow with Fastify 4.10.2
     server.close();
@@ -647,7 +659,7 @@ describe('body methods', () => {
     const response = get(url);
     expect(await response.json()).toEqual({ accept: 'application/json' });
     // eslint-disable-next-line unicorn/no-await-expression-member
-    await expect((await response).text()).rejects.toThrow(bodyAlreadyUsedError(url));
+    await expect((await response).text()).rejects.toThrow(bodyAlreadyUsedError);
 
     // FIXME await close() is too slow with Fastify 4.10.2
     server.close();
@@ -657,11 +669,24 @@ describe('body methods', () => {
 test('cannot connect', async () => {
   const url = 'http://localhost/';
 
-  const nodeFetchRequestFailedError = `request to ${url} failed, reason: connect ECONNREFUSED 127.0.0.1:80`;
-  const whatwgFetchRequestFailedError = 'Network request failed';
-  const requestFailedError = isWhatwgFetch
-    ? whatwgFetchRequestFailedError
-    : nodeFetchRequestFailedError;
+  let requestFailedError = '';
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      requestFailedError = `request to ${url} failed, reason: connect ECONNREFUSED 127.0.0.1:80`;
+      break;
+    }
+    case 'whatwg-fetch': {
+      requestFailedError = 'Network request failed';
+      break;
+    }
+    case 'undici': {
+      requestFailedError = 'fetch failed';
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
 
   // Avoid console to be polluted with whatwg-fetch "Error: connect ECONNREFUSED"
   const consoleSpy = jest.spyOn(console, 'error').mockImplementation();
@@ -671,12 +696,12 @@ test('cannot connect', async () => {
   } catch (e) {
     assert(e instanceof Error);
     /* eslint-disable jest/no-conditional-expect */
-    expect(e.name).toEqual(isWhatwgFetch ? 'TypeError' : 'FetchError');
+    expect(e.name).toEqual(process.env.FETCH === 'node-fetch' ? 'FetchError' : 'TypeError');
     expect(e.message).toEqual(requestFailedError);
     /* eslint-enable jest/no-conditional-expect */
   }
 
-  expect(consoleSpy).toHaveBeenCalledTimes(isWhatwgFetch ? 1 : 0);
+  expect(consoleSpy).toHaveBeenCalledTimes(process.env.FETCH === 'whatwg-fetch' ? 1 : 0);
 
   consoleSpy.mockRestore();
 });
diff --git a/src/createHttpError.test.ts b/src/createHttpError.test.ts
index bc9665f..d6ef489 100644
--- a/src/createHttpError.test.ts
+++ b/src/createHttpError.test.ts
@@ -1,12 +1,12 @@
 /* eslint-disable unicorn/no-null, jest/no-conditional-expect */
 
+import assert from 'node:assert';
 import { Readable } from 'node:stream';
 
 import { entriesToObject } from './utils/entriesToObject';
-import { isWhatwgFetch } from './utils/isWhatwgFetch';
 import { createHttpError, createJSONHttpError } from './createHttpError';
 
-const redirected = isWhatwgFetch ? undefined : false;
+const redirected = process.env.FETCH === 'whatwg-fetch' ? undefined : false;
 
 // "new Response()" gives a 200 response:
 // {
@@ -54,10 +54,51 @@ const redirected = isWhatwgFetch ? undefined : false;
 // - Microsoft Edge 44 (EdgeHTML 18)
 // - IE 11: 'Response' is undefined
 
+function checkBody(body: Body['body']) {
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      expect(body).toEqual(expect.any(Readable));
+      break;
+    }
+    case 'whatwg-fetch': {
+      expect(body).toEqual(undefined);
+      break;
+    }
+    case 'undici': {
+      expect(body).toEqual(expect.any(ReadableStream));
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
+}
+
+function checkBodyUsedWithNoBody(bodyUsed: Body['bodyUsed']) {
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      // FIXME https://github.com/node-fetch/node-fetch/issues/1684
+      expect(bodyUsed).toEqual(true);
+      break;
+    }
+    case 'whatwg-fetch': {
+      expect(bodyUsed).toEqual(true);
+      break;
+    }
+    case 'undici': {
+      expect(bodyUsed).toEqual(false);
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
+}
+
 test('new Response()', async () => {
   const response = new Response();
   // https://github.com/github/fetch/issues/746
-  expect(response.body).toEqual(isWhatwgFetch ? undefined : null); // Should be null
+  expect(response.body).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : null); // Should be null
   expect(response.bodyUsed).toEqual(false);
   expect(entriesToObject(response.headers)).toEqual({});
   expect(response.ok).toEqual(true);
@@ -68,13 +109,12 @@ test('new Response()', async () => {
   expect(response.url).toEqual('');
 
   expect(await response.text()).toEqual('');
-  expect(response.bodyUsed).toEqual(true);
+  checkBodyUsedWithNoBody(response.bodyUsed);
 });
 
 test("new Response('body')", async () => {
   const response = new Response('body');
-  // https://github.com/github/fetch/issues/746
-  expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+  checkBody(response.body);
   expect(response.bodyUsed).toEqual(false);
   expect(entriesToObject(response.headers)).toEqual({
     'content-type': 'text/plain;charset=UTF-8'
@@ -92,18 +132,18 @@ test("new Response('body')", async () => {
 
 test('Response.error()', async () => {
   const response = Response.error();
-  expect(response.body).toEqual(isWhatwgFetch ? undefined : null); // Should be null
+  expect(response.body).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : null); // Should be null
   expect(response.bodyUsed).toEqual(false);
   expect(entriesToObject(response.headers)).toEqual({});
   expect(response.ok).toEqual(false);
-  expect(response.redirected).toEqual(isWhatwgFetch ? undefined : false); // Should be false
+  expect(response.redirected).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : false); // Should be false
   expect(response.status).toEqual(0);
   expect(response.statusText).toEqual('');
   expect(response.type).toEqual('error');
   expect(response.url).toEqual('');
 
   expect(await response.text()).toEqual('');
-  expect(response.bodyUsed).toEqual(true);
+  checkBodyUsedWithNoBody(response.bodyUsed);
 });
 
 test('200 OK', async () => {
@@ -111,7 +151,7 @@ test('200 OK', async () => {
     const { name, message, response } = createHttpError('body', 200, 'OK');
     expect(name).toEqual('HttpError');
     expect(message).toEqual('OK');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'text/plain;charset=UTF-8'
@@ -131,7 +171,7 @@ test('200 OK', async () => {
     const { name, message, response } = createJSONHttpError({ body: true }, 200, 'OK');
     expect(name).toEqual('HttpError');
     expect(message).toEqual('OK');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'application/json'
@@ -153,7 +193,7 @@ test('204 No Content', async () => {
     const { name, message, response } = createHttpError(undefined, 204, 'No Content');
     expect(name).toEqual('HttpError');
     expect(message).toEqual('No Content');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : null);
+    expect(response.body).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : null);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({});
     expect(response.ok).toEqual(true);
@@ -164,27 +204,30 @@ test('204 No Content', async () => {
     expect(response.url).toEqual('');
 
     expect(await response.text()).toEqual('');
-    expect(response.bodyUsed).toEqual(true);
+    checkBodyUsedWithNoBody(response.bodyUsed);
   }
 
-  {
-    const { name, message, response } = createJSONHttpError({}, 204, 'No Content');
-    expect(name).toEqual('HttpError');
-    expect(message).toEqual('No Content');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
-    expect(response.bodyUsed).toEqual(false);
-    expect(entriesToObject(response.headers)).toEqual({
-      'content-type': 'application/json'
-    });
-    expect(response.ok).toEqual(true);
-    expect(response.redirected).toEqual(redirected);
-    expect(response.status).toEqual(204);
-    expect(response.statusText).toEqual('No Content');
-    expect(response.type).toEqual('default');
-    expect(response.url).toEqual('');
-
-    expect(await response.json()).toEqual({});
-    expect(response.bodyUsed).toEqual(true);
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      // FIXME https://github.com/node-fetch/node-fetch/issues/1685
+      expect(() => createJSONHttpError({}, 204, 'No Content')).not.toThrow();
+      break;
+    }
+    case 'whatwg-fetch': {
+      // FIXME https://github.com/github/fetch/issues/1213
+      expect(() => createJSONHttpError({}, 204, 'No Content')).not.toThrow();
+      break;
+    }
+    case 'undici': {
+      // FIXME Chrome 107: "TypeError: Failed to construct 'Response': Response with null body status cannot have body"
+      expect(() => createJSONHttpError({}, 204, 'No Content')).toThrow(
+        'Response constructor: Invalid response status code 204'
+      );
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
   }
 });
 
@@ -193,7 +236,7 @@ test('404 Not Found', async () => {
     const { name, message, response } = createHttpError('error', 404, 'Not Found');
     expect(name).toEqual('HttpError');
     expect(message).toEqual('Not Found');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'text/plain;charset=UTF-8'
@@ -213,7 +256,7 @@ test('404 Not Found', async () => {
     const { name, message, response } = createJSONHttpError({ error: 404 }, 404, 'Not Found');
     expect(name).toEqual('HttpError');
     expect(message).toEqual('Not Found');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'application/json'
@@ -235,7 +278,7 @@ test('no statusText', async () => {
     const { name, message, response } = createHttpError('body', 200);
     expect(name).toEqual('HttpError');
     expect(message).toEqual('200');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'text/plain;charset=UTF-8'
@@ -255,7 +298,7 @@ test('no statusText', async () => {
     const { name, message, response } = createJSONHttpError({ body: true }, 200);
     expect(name).toEqual('HttpError');
     expect(message).toEqual('200');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'application/json'
@@ -272,19 +315,66 @@ test('no statusText', async () => {
   }
 });
 
+test('status 0', async () => {
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      // FIXME https://github.com/node-fetch/node-fetch/issues/1685
+      expect(() => createHttpError('body', 0)).not.toThrow();
+      break;
+    }
+    case 'whatwg-fetch': {
+      // FIXME https://github.com/github/fetch/issues/1213
+      expect(() => createHttpError('body', 0)).not.toThrow();
+      break;
+    }
+    case 'undici': {
+      expect(() => createHttpError('body', 0)).toThrow(
+        'init["status"] must be in the range of 200 to 599, inclusive.'
+      );
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
+
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      // FIXME https://github.com/node-fetch/node-fetch/issues/1685
+      expect(() => createJSONHttpError({ body: true }, 0)).not.toThrow();
+      break;
+    }
+    case 'whatwg-fetch': {
+      // FIXME https://github.com/github/fetch/issues/1213
+      expect(() => createJSONHttpError({ body: true }, 0)).not.toThrow();
+      break;
+    }
+    case 'undici': {
+      expect(() => createJSONHttpError({ body: true }, 0)).toThrow(
+        'init["status"] must be in the range of 200 to 599, inclusive.'
+      );
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
+});
+
 test('no status', async () => {
   {
+    // @ts-ignore
     const { name, message, response } = createHttpError('body');
     expect(name).toEqual('HttpError');
-    expect(message).toEqual('0');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    expect(message).toEqual('200');
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'text/plain;charset=UTF-8'
     });
-    expect(response.ok).toEqual(false);
+    expect(response.ok).toEqual(true);
     expect(response.redirected).toEqual(redirected);
-    expect(response.status).toEqual(0);
+    expect(response.status).toEqual(200);
     expect(response.statusText).toEqual('');
     expect(response.type).toEqual('default');
     expect(response.url).toEqual('');
@@ -294,17 +384,18 @@ test('no status', async () => {
   }
 
   {
+    // @ts-ignore
     const { name, message, response } = createJSONHttpError({ body: true });
     expect(name).toEqual('HttpError');
-    expect(message).toEqual('0');
-    expect(response.body).toEqual(isWhatwgFetch ? undefined : expect.any(Readable));
+    expect(message).toEqual('200');
+    checkBody(response.body);
     expect(response.bodyUsed).toEqual(false);
     expect(entriesToObject(response.headers)).toEqual({
       'content-type': 'application/json'
     });
-    expect(response.ok).toEqual(false);
+    expect(response.ok).toEqual(true);
     expect(response.redirected).toEqual(redirected);
-    expect(response.status).toEqual(0);
+    expect(response.status).toEqual(200);
     expect(response.statusText).toEqual('');
     expect(response.type).toEqual('default');
     expect(response.url).toEqual('');
@@ -315,19 +406,20 @@ test('no status', async () => {
 });
 
 test('no params', async () => {
+  // @ts-ignore
   const { name, message, response } = createHttpError();
   expect(name).toEqual('HttpError');
-  expect(message).toEqual('0');
-  expect(response.body).toEqual(isWhatwgFetch ? undefined : null);
+  expect(message).toEqual('200');
+  expect(response.body).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : null);
   expect(response.bodyUsed).toEqual(false);
   expect(entriesToObject(response.headers)).toEqual({});
-  expect(response.ok).toEqual(false);
+  expect(response.ok).toEqual(true);
   expect(response.redirected).toEqual(redirected);
-  expect(response.status).toEqual(0);
+  expect(response.status).toEqual(200);
   expect(response.statusText).toEqual('');
   expect(response.type).toEqual('default');
   expect(response.url).toEqual('');
 
   expect(await response.text()).toEqual('');
-  expect(response.bodyUsed).toEqual(true);
+  checkBodyUsedWithNoBody(response.bodyUsed);
 });
diff --git a/src/createHttpError.ts b/src/createHttpError.ts
index d615bff..19de0f0 100644
--- a/src/createHttpError.ts
+++ b/src/createHttpError.ts
@@ -8,7 +8,7 @@ import { HttpError } from './HttpError';
  *
  * @see {@link createJSONHttpError()}
  */
-export function createHttpError(body?: BodyInit, status = 0, statusText?: string) {
+export function createHttpError(body: BodyInit | undefined, status: number, statusText?: string) {
   return new HttpError(
     new Response(body, {
       status,
@@ -24,8 +24,9 @@ export function createHttpError(body?: BodyInit, status = 0, statusText?: string
  */
 // Record<string, unknown> is compatible with "type" not with "interface": "Index signature is missing in type 'MyInterface'"
 // Best alternative is object, why? https://stackoverflow.com/a/58143592
-export function createJSONHttpError(body: object, status = 0, statusText?: string) {
+export function createJSONHttpError(body: object, status: number, statusText?: string) {
   return new HttpError(
+    // FIXME Replace with [new Response.json()](https://twitter.com/lcasdev/status/1564598435772342272)
     new Response(JSON.stringify(body), {
       status,
       statusText,
diff --git a/src/createResponsePromise.test.ts b/src/createResponsePromise.test.ts
index fa6b613..419c53b 100644
--- a/src/createResponsePromise.test.ts
+++ b/src/createResponsePromise.test.ts
@@ -1,5 +1,6 @@
+import assert from 'node:assert';
+
 import { entriesToObject } from './utils/entriesToObject';
-import { isWhatwgFetch } from './utils/isWhatwgFetch';
 import { wait } from './utils/wait';
 import { createJSONResponsePromise, createResponsePromise } from './createResponsePromise';
 import * as Http from './Http';
@@ -14,7 +15,7 @@ test('default Response object', async () => {
     'content-type': 'text/plain;charset=UTF-8'
   });
   expect(response.ok).toEqual(true);
-  expect(response.redirected).toEqual(isWhatwgFetch ? undefined : false);
+  expect(response.redirected).toEqual(process.env.FETCH === 'whatwg-fetch' ? undefined : false);
   expect(response.status).toEqual(200);
   expect(response.statusText).toEqual('');
   expect(response.url).toEqual('');
@@ -32,7 +33,7 @@ describe('body methods', () => {
     const blob = await responsePromise.blob();
     expect(blob.size).toEqual(4);
     // FIXME https://github.com/jsdom/jsdom/issues/2555
-    if (!isWhatwgFetch) {
+    if (process.env.FETCH !== 'whatwg-fetch') {
       // eslint-disable-next-line jest/no-conditional-expect
       expect(await blob.text()).toEqual('test');
     }
@@ -73,11 +74,24 @@ describe('body methods', () => {
   });
 
   // https://github.com/whatwg/fetch/issues/1147
-  const nodeFetchBodyAlreadyUsedError = 'body used already for: ';
-  const whatwgFetchBodyAlreadyUsedError = 'Already read';
-  const bodyAlreadyUsedError = isWhatwgFetch
-    ? whatwgFetchBodyAlreadyUsedError
-    : nodeFetchBodyAlreadyUsedError;
+  let bodyAlreadyUsedError = '';
+  switch (process.env.FETCH) {
+    case 'node-fetch': {
+      bodyAlreadyUsedError = 'body used already for: ';
+      break;
+    }
+    case 'whatwg-fetch': {
+      bodyAlreadyUsedError = 'Already read';
+      break;
+    }
+    case 'undici': {
+      bodyAlreadyUsedError = 'Body is unusable';
+      break;
+    }
+    default: {
+      assert(false, `Unknown FETCH env '${process.env.FETCH}'`);
+    }
+  }
 
   test('multiple body calls using helpers', async () => {
     const responsePromise = createJSONResponsePromise({ test: 'true' });
diff --git a/src/createTestServer/createTestServer.test.ts b/src/createTestServer/createTestServer.test.ts
index c77c518..c297a54 100644
--- a/src/createTestServer/createTestServer.test.ts
+++ b/src/createTestServer/createTestServer.test.ts
@@ -1,4 +1,3 @@
-import { isWhatwgFetch } from '../utils/isWhatwgFetch';
 import { createTestServer } from './createTestServer';
 
 const path = '/';
@@ -56,8 +55,8 @@ test.skip('respond to HTTP/2 requests', async () => {
   server.close();
 });
 
-// node-fetch does not care about CORS
-if (isWhatwgFetch) {
+// node-fetch & undici don't care about CORS
+if (process.env.FETCH === 'whatwg-fetch') {
   test('CORS fail', async () => {
     const consoleSpy = jest.spyOn(console, 'error').mockImplementation();
 
diff --git a/src/utils/isWhatwgFetch.ts b/src/utils/isWhatwgFetch.ts
deleted file mode 100644
index 3183d45..0000000
--- a/src/utils/isWhatwgFetch.ts
+++ /dev/null
@@ -1,2 +0,0 @@
-// https://github.com/github/fetch/blob/v3.5.0/fetch.js#L598
-export const isWhatwgFetch = (fetch as any).polyfill === true;