Confidently test your Next.js API routes in an isolated Next-like environment
Trying to unit test your Next.js API routes? Tired of hacking something
together with express or node-mocks-http or writing a bunch of boring dummy
infra just to get some passing tests? And what does a "passing test" mean anyway
when your handlers aren't receiving actual NextRequest objects and
aren't being run by Next.js itself?
Next.js patches the global
fetchfunction, for instance. If your tests aren't doing the same, you're making space for bugs!
Is it vexing that everything explodes when your App Router handlers call
headers() or cookies() or any of the other route-specific helper
functions? Or maybe you want your Pages Router handlers to receive
actual NextApiRequest and NextApiResponse objects?
Sound interesting? Then want no longer! 🤩
next-test-api-route-handler (NTARH) uses Next.js's
internal resolvers to precisely emulate route handling. To guarantee stability,
this package is automatically tested against each release of Next.js
and Node.js. Go forth and test confidently!
✨ ✨
Note that App Router support begins with [email protected] (why?)
npm install --save-dev next-test-api-route-handlerSee the appendix for legacy Next.js support options.
Also see the appendix if you're using
jestandjest-environment-jsdom.
Important
NTARH must always be the first import in your test file. This is due to the way Next.js is written and distributed. See the appendix for technical details.
// ESM
import { testApiHandler } from 'next-test-api-route-handler'; // ◄ Must be first
... all other imports ...// CJS
const { testApiHandler } = require('next-test-api-route-handler'); // ◄ Must be first
... all other imports .../* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler'; // ◄ Must be first import
// Import the handler under test from the app directory
import * as appHandler from '../app/your-endpoint/route';
it('does what I want', async () => {
await testApiHandler({
appHandler,
// requestPatcher is optional
requestPatcher(request) {
request.headers.set('key', process.env.SPECIAL_TOKEN);
},
// responsePatcher is optional
async responsePatcher(response) {
const json = await response.json();
return Response.json(
json.apiSuccess ? { hello: 'world!' } : { goodbye: 'cruel world' }
);
},
async test({ fetch }) {
const res = await fetch({ method: 'POST', body: 'dummy-data' });
await expect(res.json()).resolves.toStrictEqual({ hello: 'world!' }); // ◄ Passes!
}
});
});/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler'; // ◄ Must be first import
// Import the handler under test from the app directory
import * as edgeHandler from '../app/your-edge-endpoint/route';
it('does what I want', async function () {
// NTARH supports optionally typed response data via TypeScript generics:
await testApiHandler<{ success: boolean }>({
// Only appHandler supports edge functions. The pagesHandler prop does not!
appHandler: edgeHandler,
// requestPatcher is optional
requestPatcher(request) {
return new Request(request, {
body: dummyReadableStream,
duplex: 'half'
});
},
async test({ fetch }) {
// The next line would cause TypeScript to complain:
// const { luck: success } = await (await fetch()).json();
await expect((await fetch()).json()).resolves.toStrictEqual({
success: true // ◄ Passes!
});
}
});
});/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler'; // ◄ Must be first import
// Import the handler under test and its config from the pages/api directory
import * as pagesHandler from '../pages/api/your-endpoint';
it('does what I want', async () => {
// NTARH supports optionally typed response data via TypeScript generics:
await testApiHandler<{ hello: string }>({
pagesHandler,
requestPatcher: (req) => {
req.headers = { key: process.env.SPECIAL_TOKEN };
},
test: async ({ fetch }) => {
const res = await fetch({ method: 'POST', body: 'data' });
// The next line would cause TypeScript to complain:
// const { goodbye: hello } = await res.json();
const { hello } = await res.json();
expect(hello).toBe('world'); // ◄ Passes!
}
});
});NTARH exports a single function, testApiHandler(options), that accepts an
options object as its only parameter.
At minimum, options must contain the following properties:
- At least one of the
appHandlerorpagesHandleroptions, but not both. - The
testoption.
For example:
Caution
Ensuring testApiHandler is imported before any Next.js package (like
'next/headers' below) is crucial to the proper function of NTARH. Doing otherwise
will result in undefined behavior.
import { testApiHandler } from 'next-test-api-route-handler';
import { headers } from 'next/headers';
await testApiHandler({
appHandler: {
dynamic: 'force-dynamic',
GET(_request) {
return Response.json(
{
// Yep, those fancy helper functions work too!
hello: headers().get('x-hello')
},
{ status: 200 }
);
}
},
async test({ fetch }) {
await expect(
(await fetch({ headers: { 'x-hello': 'world' } })).json()
).resolves.toStrictEqual({
hello: 'world'
});
}
});⪢ API reference:
appHandler
The actual route handler under test (usually imported from app/*). It should
be an object and/or exported module containing one or more valid uppercase HTTP
method names as keys, each with an async handling function that
accepts a NextRequest and a context (i.e. { params }) as its two
parameters. The object or module can also export other configuration settings
recognized by Next.js.
await testApiHandler({
params: { id: 5 },
appHandler: {
async POST(request, { params: { id } }) {
return Response.json(
{ special: request.headers.get('x-special-header'), id },
{ status: 200 }
);
}
},
async test({ fetch }) {
expect((await fetch({ method: 'POST' })).status).toBe(200);
const result2 = await fetch({
method: 'POST',
headers: { 'x-special-header': 'x' }
});
expect(result2.json()).toStrictEqual({ special: 'x', id: 5 });
}
});See also: rejectOnHandlerError and the section Working Around Next.js
fetch Patching.
⪢ API reference:
pagesHandler
The actual route handler under test (usually imported from pages/api/*). It
should be an async function that accepts NextApiRequest and
NextApiResponse objects as its two parameters.
await testApiHandler({
params: { id: 5 },
pagesHandler: (req, res) => res.status(200).send({ id: req.query.id }),
test: async ({ fetch }) =>
expect((await fetch({ method: 'POST' })).json()).resolves.toStrictEqual({
id: 5
})
});See also: rejectOnHandlerError.
⪢ API reference:
test
An async or promise-returning function wherein test assertions can be run. This
function receives one destructured parameter: fetch, which is a wrapper around
Node's global fetch function. Use this to send HTTP requests to the
handler under test.
Caution
Note that fetch's resource parameter, i.e. the first parameter in fetch(...),
is omitted.
Starting with version 4.0.4, NTARH sets the fetch(...) options
parameter's redirect property to 'manual' by default. This prevents
the WHATWG/undici fetch function from throwing a
fetch failed/redirect count exceeded error.
If you want to change this value, call fetch with your own custom options
parameter, e.g. fetch({ redirect: 'error' }).
Starting with version 4.0.0, NTARH ships with Mock Service Worker (msw)
support by adding the x-msw-intention: "bypass" and
x-msw-bypass: "true" headers to all requests.
If necessary, you can override this behavior by setting the appropriate headers
to some other value (e.g. "none") via fetch's customInit parameter (not
requestPatcher). This comes in handy when testing functionality like
arbitrary response redirection (or via the Pages Router).
For example:
import { testApiHandler } from 'next-test-api-route-handler';
import { http, passthrough, HttpResponse } from 'msw';
import { setupServer } from 'msw/node';
const server = setupServer(/* ... */);
beforeAll(() => server.listen({ onUnhandledRequest: 'error' }));
afterEach(() => {
server.resetHandlers();
});
afterAll(() => server.close());
it('redirects a shortened URL to the real URL', async () => {
expect.hasAssertions();
// e.g. https://xunn.at/gg => https://www.google.com/search?q=next-test-api-route-handler
// shortId would be "gg"
// realLink would be https://www.google.com/search?q=next-test-api-route-handler
const { shortId, realLink } = getUriEntry();
const realUrl = new URL(realLink);
await testApiHandler({
appHandler,
params: { shortId },
test: async ({ fetch }) => {
server.use(
http.get('*', async ({ request }) => {
return request.url === realUrl.href
? HttpResponse.json({ it: 'worked' }, { status: 200 })
: passthrough();
})
);
const res = await fetch({
headers: { 'x-msw-intention': 'none' } // <==
});
await expect(res.json()).resolves.toMatchObject({ it: 'worked' });
expect(res.status).toBe(200);
}
});
});As of version 2.3.0, the response object returned by fetch() includes a
non-standard cookies field containing an array of objects representing
set-cookie response header(s) parsed by the cookie package. Use
the cookies field to easily access a response's cookie data in your tests.
Here's an example taken straight from the unit tests:
import { testApiHandler } from 'next-test-api-route-handler';
it('handles multiple set-cookie headers', async () => {
expect.hasAssertions();
await testApiHandler({
pagesHandler: (_, res) => {
// Multiple calls to setHeader('Set-Cookie', ...) overwrite previous, so
// we have to set the Set-Cookie header properly
res
.setHeader('Set-Cookie', [
serializeCookieHeader('access_token', '1234', {
expires: new Date()
}),
serializeCookieHeader('REFRESH_TOKEN', '5678')
])
.status(200)
.send({});
},
test: async ({ fetch }) => {
expect((await fetch()).status).toBe(200);
await expect((await fetch()).json()).resolves.toStrictEqual({});
expect((await fetch()).cookies).toStrictEqual([
{
access_token: '1234',
// Lowercased cookie property keys are available
expires: expect.any(String),
// Raw cookie property keys are also available
Expires: expect.any(String)
},
{ refresh_token: '5678', REFRESH_TOKEN: '5678' }
]);
}
});
});⪢ API reference:
rejectOnHandlerError
As of version 2.3.0, unhandled errors in the pagesHandler/appHandler
function are kicked up to Next.js to handle.
Important
This means testApiHandler will NOT reject or throw if an unhandled error occurs
in pagesHandler/appHandler, which typically includes failing expect() assertions.
Instead, the response returned by fetch() in your test function will have a
HTTP 500 status thanks to how Next.js deals with unhandled errors in
production. Prior to 2.3.0, NTARH's behavior on unhandled errors and
elsewhere was inconsistent. Version 3.0.0 further improved error handling,
ensuring no errors slip by uncaught.
To guard against false negatives, you can do either of the following:
- Make sure the status of the
fetch()response is what you're expecting:
const res = await fetch();
...
// For this test, a 403 status is what we wanted
expect(res.status).toBe(403);
...
const res2 = await fetch();
...
// Later, we expect an "unhandled" error
expect(res2.status).toBe(500);- If you're using version
>=3.0.0, you can userejectOnHandlerErrorto tell NTARH to intercept unhandled handler errors and reject the promise returned bytestApiHandlerinstead of relying on Next.js to respond withHTTP 500. This is especially useful if you haveexpect()assertions inside your handler function:
await expect(
testApiHandler({
rejectOnHandlerError: true, // <==
pagesHandler: (_req, res) => {
res.status(200);
throw new Error('bad bad not good');
},
test: async ({ fetch }) => {
const res = await fetch();
// By default, res.status would be 500...
//expect(res.status).toBe(500);
}
})
// ...but since we used rejectOnHandlerError, the whole promise rejects
// instead
).rejects.toThrow('bad not good');
await testApiHandler({
rejectOnHandlerError: true, // <==
appHandler: {
async GET(request) {
// Suppose this expectation fails
await expect(backend.getSomeStuff(request)).resolves.toStrictEqual(
someStuff
);
return new Response(null, { status: 200 });
}
},
test: async ({ fetch }) => {
await fetch();
// By default, res.status would be 500 due to the failing expect(). If we
// don't also expect() a non-500 response status here, the failing
// expectation in the handler will be swallowed and the test will pass
// (a false negative).
}
});
// ...but since we used rejectOnHandlerError, the whole promise rejects
// and it is reported that the test failed, which is probably what you wanted.Tip
Manually setting the request url is usually unnecessary. Only set the url if your
handler expects it or you want to rely on query string parsing instead of
params/paramsPatcher.
⪢ API reference:
requestPatcher,url
requestPatcher is a function that receives a NextRequest object and
returns a Request instance. Use this function to edit the request
before it's injected into the handler.
Caution
Be wary returning a brand new request from requestPatcher (i.e. new NextRequest(newUrl)
instead of new NextRequest(newUrl, oldRequest)), especially one that is missing
standard headers added by fetch(...). If you're getting strange JSON-related
errors or hanging tests, ensure this is not the cause.
The returned Request instance will be wrapped with NextRequest if
it is not already an instance of NextRequest, i.e.:
const returnedRequest = (await requestPatcher?.(request)) || request;
const nextRequest = new NextRequest(returnedRequest, { ... });If you're only setting the request url, use the url shorthand instead:
await testApiHandler({
// requestPatcher: (request) => new Request('ntarh:///my-url?some=query', request),
url: '/my-url?some=query'
});Note
Unlike the Pages Router's NextApiRequest type, the App Router's NextRequest
class does not support relative URLs. Therefore, whenever you pass a relative
url string via the url shorthand (e.g. { url: '/my-url?some=query' }), NTARH
will wrap that url like so: new URL(url, 'ntarh://'). In this case, your requests
will have urls like ntarh:///my-url?some=query.
By default, when initializing the NextRequest object passed to your handler,
if a URL with an empty pathname is encountered, NTARH sets said URL's
pathname to "/" on your behalf. Additionally, if said URL is missing host
and/or protocol, NTARH sets host to "" and protocol to "ntarh:".
If you want your handler to receive the URL string and resulting
NextRequest::nextUrl object exactly as you've typed it, use requestPatcher,
which is executed after NTARH does URL normalization.
⪢ API reference:
requestPatcher,url
requestPatcher is a function that receives an IncomingMessage. Use
this function to modify the request before it's injected into Next.js's
resolver.
If you're only setting the request url, use the url shorthand instead:
await testApiHandler({
// requestPatcher: (req) => { req.url = '/my-url?some=query'; }
url: '/my-url?some=query'
});Note that, unlike with the URL class, the url string can be relative.
⪢ API reference:
responsePatcher
responsePatcher is a function that receives the Response object
returned from appHandler and returns a Response instance. Use this
function to edit the response after your handler runs but before it's
processed by the server.
⪢ API reference:
responsePatcher
responsePatcher is a function that receives a ServerResponse object.
Use this function to edit the response before it's injected into the handler.
paramsPatcher is a function that receives an object representing "processed"
dynamic segments (aka: routes, slugs).
For example, to test a handler normally accessible from /api/user/:id requires
passing that handler a value for the "id" dynamic segment:
await testApiHandler({
paramsPatcher(params) {
params.id = 'test-id';
}
});Or:
await testApiHandler({
paramsPatcher: (params) => ({ id: 'test-id' })
});Parameters can also be passed using the params shorthand:
await testApiHandler({
params: {
id: 'test-id'
}
});Tip
Due to its simplicity, favor the params shorthand over paramsPatcher.
⪢ API reference:
paramsPatcher,params
If both paramsPatcher and the params shorthand are used, paramsPatcher
will receive params as its first argument.
Route parameters should not be confused with query string parameters, which are automatically parsed out from the url and made available via the
NextRequestargument passed to your handler.
⪢ API reference:
paramsPatcher,params
If both paramsPatcher and the params shorthand are used, paramsPatcher
will receive an object like { ...queryStringURLParams, ...params } as its
first argument.
Route parameters should not be confused with query string parameters, which are automatically parsed out from the url and added to the
paramsobject beforeparamsPatcheris evaluated.
What follows are several examples that demonstrate using NTARH with the App Router and the Pages Router.
Check out the tests for even more examples.
These examples use Next.js's App Router API.
This example is based on the official Apollo Next.js App Router integration. You can run it yourself by copying and pasting the following commands into your terminal.
The following should be run in a nix-like environment. On Windows, that's WSL. Requires
curl,node, andgit.
mkdir -p /tmp/ntarh-test/test
cd /tmp/ntarh-test
npm install --force next @apollo/server @as-integrations/next graphql-tag next-test-api-route-handler jest babel-jest @babel/core @babel/preset-env
echo 'module.exports={"presets":["next/babel"]};' > babel.config.js
mkdir -p app/api/graphql
curl -o app/api/graphql/route.js https://raw.githubusercontent.com/Xunnamius/next-test-api-route-handler/main/apollo_test_raw_app_route
curl -o test/integration.test.js https://raw.githubusercontent.com/Xunnamius/next-test-api-route-handler/main/apollo_test_raw_app_test
npx jestThis script creates a new temporary directory, installs NTARH and configures dependencies, downloads the app route and jest test files shown below, and runs the test using jest.
The following is our new app route:
/* File: app/api/graphql/route.js */
import { ApolloServer } from '@apollo/server';
import { startServerAndCreateNextHandler } from '@as-integrations/next';
import { gql } from 'graphql-tag';
const resolvers = {
Query: {
hello: () => 'world'
}
};
const typeDefs = gql`
type Query {
hello: String
}
`;
const server = new ApolloServer({
resolvers,
typeDefs
});
const handler = startServerAndCreateNextHandler(server);
export { handler as GET, handler as POST };And with the following jest test, we ensure our route integrates with Apollo correctly:
/* File: tests/integration.test.js */
import { testApiHandler } from 'next-test-api-route-handler';
// Import the handler under test from the app/api directory
import * as appHandler from '../app/api/graphql/route';
describe('my-test (app router)', () => {
it('does what I want 1', async () => {
expect.hasAssertions();
await testApiHandler({
appHandler,
test: async ({ fetch }) => {
const query = `query { hello }`;
const res = await fetch({
method: 'POST',
headers: {
'content-type': 'application/json' // Must use correct content type
},
body: JSON.stringify({ query })
});
await expect(res.json()).resolves.toStrictEqual({
data: { hello: 'world' }
});
}
});
});
it('does what I want 2', async () => {
// Exactly the same as the above...
});
it('does what I want 3', async () => {
// Exactly the same as the above...
});
});Suppose we created a new authenticated API endpoint at app/api/authed by
cloning the Clerk App Router demo repo and following Clerk's quick-start
guide for Next.js:
/* File: app/api/authed/route.ts */
import { auth } from '@clerk/nextjs';
export async function GET() {
const { userId } = auth();
return Response.json({ isAuthed: !!userId, userId });
}How might we test that this endpoint functions as we expect?
/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler';
import * as appHandler from '../app/api/authed/route';
import type { auth } from '@clerk/nextjs';
let mockedClerkAuthReturnValue: Partial<ReturnType<typeof auth>> | undefined =
undefined;
jest.mock('@clerk/nextjs', () => {
return {
auth() {
return mockedClerkAuthReturnValue;
}
};
});
afterEach(() => {
mockedClerkAuthReturnValue = undefined;
});
it('returns isAuthed: true and a userId when authenticated', async () => {
expect.hasAssertions();
mockedClerkAuthReturnValue = { userId: 'winning' };
await testApiHandler({
appHandler,
test: async ({ fetch }) => {
await expect((await fetch()).json()).resolves.toStrictEqual({
isAuthed: true,
userId: 'winning'
});
}
});
});
it('returns isAuthed: false and nothing else when unauthenticated', async () => {
expect.hasAssertions();
mockedClerkAuthReturnValue = { userId: null };
await testApiHandler({
appHandler,
test: async ({ fetch }) => {
await expect((await fetch()).json()).resolves.toStrictEqual({
isAuthed: false,
userId: null
});
}
});
});If you're feeling more adventurous, you can transform this unit test into an
integration test (like the Apollo example above) by calling Clerk's
authMiddleware function in appHandler instead of mocking
@clerk/nextjs:
// This integration test also requires your Clerk dashboard is setup in test
// mode and your Clerk secret key information is available in process.env. Said
// information must be available BEFORE any Clerk packages are imported! You
// will also have to setup authMiddleware properly in ../middleware.ts
/* ... same imports as before ... */
// Also import our Next.js middleware
import { default as middleware } from '../middleware';
// And we want to keep our types as tight as we can too
import type { NextRequest } from 'next/server';
const DUMMY_CLERK_USER_ID = 'user_2aqlGWnjdTRRbbBk9OdBHHbniyK';
it('returns isAuthed: true and a userId when authenticated', async () => {
expect.hasAssertions();
await testApiHandler({
rejectOnHandlerError: true,
// You may want to alter the default URL pathname like below if your Clerk
// middleware is using path-based filtering. By default, the pathname
// will always be '/' because 'ntarh://testApiHandler/' is the default url
url: 'ntarh://app/api/authed',
appHandler: {
get GET() {
return async function (...args: Parameters<typeof appHandler.GET>) {
const request = args.at(0) as unknown as NextRequest;
const middlewareResponse = await middleware(request, {
/* ... */
});
// Make sure we're not being redirected to the sign in page since
// this is a publicly available endpoint
expect(middlewareResponse.headers.get('location')).toBeNull();
expect(middlewareResponse.ok).toBe(true);
const handlerResponse = await appHandler.GET(...args);
// You could run some expectations here (since rejectOnHandlerError is
// true), or you can run your remaining expectations in the test
// function below. Either way is fine.
return handlerResponse;
};
}
},
test: async ({ fetch }) => {
await expect((await fetch()).json()).resolves.toStrictEqual({
isAuthed: true,
userId: DUMMY_CLERK_USER_ID
});
}
});
});
/* ... */You can also try calling authMiddleware in requestPatcher; however,
Clerk's middleware does its magic by importing the headers helper function
from 'next/headers', and only functions invoked within appHandler have
access to the storage context that allows Next.js's helper functions to work.
For insight into what you'd need to do to make authMiddleware callable
in requestPatcher, check out Clerk's own tests.
Suppose we have an API endpoint we use to test our application's error handling.
The endpoint responds with status code HTTP 200 for every request except the
10th, where status code HTTP 555 is returned instead.
How might we test that this endpoint responds with HTTP 555 once for every
nine HTTP 200 responses?
/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler';
// Import the handler under test from the app/api directory
import * as edgeHandler from '../app/api/unreliable';
const expectedReqPerError = 10;
it('injects contrived errors at the required rate', async () => {
expect.hasAssertions();
// Signal to the edge endpoint (which is configurable) that there should be 1
// error among every 10 requests
process.env.REQUESTS_PER_CONTRIVED_ERROR = expectedReqPerError.toString();
await testApiHandler({
appHandler: edgeHandler,
requestPatcher(request) {
// Our edge handler expects Next.js to provide geo and ip data with the
// request, so let's add some. This is also where you'd mock/emulate the
// effects of any Next.js middleware
return new NextRequest(request, {
geo: { city: 'Chicago', country: 'United States' },
ip: '110.10.77.7'
});
},
test: async ({ fetch }) => {
// Run 20 requests with REQUESTS_PER_CONTRIVED_ERROR = '10' and
// record the results
const results1 = await Promise.all(
[
...Array.from({ length: expectedReqPerError - 1 }).map(() =>
fetch({ method: 'GET' })
),
fetch({ method: 'POST' }),
...Array.from({ length: expectedReqPerError - 1 }).map(() =>
fetch({ method: 'PUT' })
),
fetch({ method: 'DELETE' })
].map((p) => p.then((r) => r.status))
);
process.env.REQUESTS_PER_CONTRIVED_ERROR = '0';
// Run 10 requests with REQUESTS_PER_CONTRIVED_ERROR = '0' and record the
// results
const results2 = await Promise.all(
Array.from({ length: expectedReqPerError }).map(() =>
fetch().then((r) => r.status)
)
);
// We expect results1 to be an array with eighteen `200`s and two
// `555`s in any order
//
// https://github.com/jest-community/jest-extended#toincludesamemembersmembers
// because responses could be received out of order
expect(results1).toIncludeSameMembers([
...Array.from({ length: expectedReqPerError - 1 }).map(() => 200),
555,
...Array.from({ length: expectedReqPerError - 1 }).map(() => 200),
555
]);
// We expect results2 to be an array with ten `200`s
expect(results2).toStrictEqual([
...Array.from({ length: expectedReqPerError }).map(() => 200)
]);
}
});
});These examples use Next.js's Pages Router API.
This example uses the official Next.js Apollo demo. You can easily run it yourself by copying and pasting the following commands into your terminal.
The following should be run in a nix-like environment. On Windows, that's WSL. Requires
curl,node, andgit.
git clone --depth=1 https://github.com/vercel/next.js /tmp/ntarh-test
cd /tmp/ntarh-test/examples/api-routes-apollo-server-and-client
npm install --force
npm install --force next-test-api-route-handler jest babel-jest @babel/core @babel/preset-env
# You could test with an older version of Next.js if you want, e.g.:
# npm install --force [email protected]
# Or even older:
# npm install --force [email protected] next-server
echo 'module.exports={"presets":["next/babel"]};' > babel.config.js
mkdir test
curl -o test/integration.test.js https://raw.githubusercontent.com/Xunnamius/next-test-api-route-handler/main/apollo_test_raw
npx jestThis script clones the Next.js repository, installs NTARH and configures dependencies, downloads the jest test file shown below, and runs it using jest to ensure our route integrates with Apollo correctly.
Important
Note that passing the route configuration object (imported below as config)
through to NTARH and setting request.url to the proper value may be necessary
when testing Apollo endpoints using the Pages Router.
/* File: examples/api-routes-apollo-server-and-client/tests/integration.test.js */
import { testApiHandler } from 'next-test-api-route-handler';
// Import the handler under test from the pages/api directory
import * as pagesHandler from '../pages/api/graphql';
describe('my-test (pages router)', () => {
it('does what I want 1', async () => {
expect.hasAssertions();
await testApiHandler({
pagesHandler,
url: '/api/graphql', // Set the request url to the path graphql expects
test: async ({ fetch }) => {
const query = `query ViewerQuery {
viewer {
id
name
status
}
}`;
const res = await fetch({
method: 'POST',
headers: {
'content-type': 'application/json' // Must use correct content type
},
body: JSON.stringify({ query })
});
await expect(res.json()).resolves.toStrictEqual({
data: { viewer: { id: '1', name: 'John Smith', status: 'cached' } }
});
}
});
});
it('does what I want 2', async () => {
// Exactly the same as the above...
});
it('does what I want 3', async () => {
// Exactly the same as the above...
});
});Suppose we have an authenticated API endpoint our application uses to search for flights. The endpoint responds with an array of flights satisfying the query.
How might we test that this endpoint returns flights in our database as expected?
/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler';
import { DUMMY_API_KEY as KEY, getFlightData, RESULT_SIZE } from '../backend';
import * as pagesHandler from '../pages/api/v3/flights/search';
import type { PageConfig } from 'next';
it('returns expected public flights with respect to match', async () => {
expect.hasAssertions();
// Get the flight data currently in the test database
const expectedFlights = getFlightData();
// Take any JSON object and stringify it into a URL-ready string
const encode = (o: Record<string, unknown>) =>
encodeURIComponent(JSON.stringify(o));
// This function will return in order the URIs we're interested in testing
// against our handler. Query strings are parsed by NTARH automatically.
//
// NOTE: setting the request url manually using encode(), while valid, is
// unnecessary here; we could have used `params` or `paramsPatcher` to do this
// more easily without explicitly setting a dummy request url.
//
// Example URI for `https://site.io/path?param=yes` would be `/path?param=yes`
const genUrl = (function* () {
// For example, the first should match all the flights from Spirit airlines!
yield `/?match=${encode({ airline: 'Spirit' })}`;
yield `/?match=${encode({ type: 'departure' })}`;
yield `/?match=${encode({ landingAt: 'F1A' })}`;
yield `/?match=${encode({ seatPrice: 500 })}`;
yield `/?match=${encode({ seatPrice: { $gt: 500 } })}`;
yield `/?match=${encode({ seatPrice: { $gte: 500 } })}`;
yield `/?match=${encode({ seatPrice: { $lt: 500 } })}`;
yield `/?match=${encode({ seatPrice: { $lte: 500 } })}`;
})();
await testApiHandler({
// Patch the request object to include our dummy URI
requestPatcher: (req) => {
req.url = genUrl.next().value || undefined;
// Could have done this instead of `fetch({ headers: { KEY }})` below:
// req.headers = { KEY };
},
pagesHandler,
test: async ({ fetch }) => {
// 8 URLs from genUrl means 8 calls to fetch:
const responses = await Promise.all(
Array.from({ length: 8 }).map(() =>
fetch({ headers: { KEY } }).then(async (r) => [
r.status,
await r.json()
])
)
);
// We expect all of the responses to be 200
expect(responses.some(([status]) => status !== 200)).toBe(false);
// We expect the array of flights returned to match our
// expectations given we already know what dummy data will be
// returned:
// https://github.com/jest-community/jest-extended#toincludesamemembersmembers
// because responses could be received out of order
expect(responses.map(([, r]) => r.flights)).toIncludeSameMembers([
expectedFlights
.filter((f) => f.airline === 'Spirit')
.slice(0, RESULT_SIZE),
expectedFlights
.filter((f) => f.type === 'departure')
.slice(0, RESULT_SIZE),
expectedFlights
.filter((f) => f.landingAt === 'F1A')
.slice(0, RESULT_SIZE),
expectedFlights
.filter((f) => f.seatPrice === 500)
.slice(0, RESULT_SIZE),
expectedFlights.filter((f) => f.seatPrice > 500).slice(0, RESULT_SIZE),
expectedFlights.filter((f) => f.seatPrice >= 500).slice(0, RESULT_SIZE),
expectedFlights.filter((f) => f.seatPrice < 500).slice(0, RESULT_SIZE),
expectedFlights.filter((f) => f.seatPrice <= 500).slice(0, RESULT_SIZE)
]);
}
});
// We expect these two to fail with 400 errors
await testApiHandler({
pagesHandler,
url: `/?match=${encode({ ffms: { $eq: 500 } })}`,
test: async ({ fetch }) =>
expect((await fetch({ headers: { KEY } })).status).toBe(400)
});
await testApiHandler({
pagesHandler,
url: `/?match=${encode({ bad: 500 })}`,
test: async ({ fetch }) =>
expect((await fetch({ headers: { KEY } })).status).toBe(400)
});
});Suppose we have an API endpoint we use to test our application's error handling.
The endpoint responds with status code HTTP 200 for every request except the
10th, where status code HTTP 555 is returned instead.
How might we test that this endpoint responds with HTTP 555 once for every
nine HTTP 200 responses?
/* File: test/unit.test.ts */
import { testApiHandler } from 'next-test-api-route-handler';
// Import the handler under test from the pages/api directory
import * as pagesHandler from '../pages/api/unreliable';
const expectedReqPerError = 10;
it('injects contrived errors at the required rate', async () => {
expect.hasAssertions();
// Signal to the endpoint (which is configurable) that there should be 1
// error among every 10 requests
process.env.REQUESTS_PER_CONTRIVED_ERROR = expectedReqPerError.toString();
await testApiHandler({
pagesHandler,
test: async ({ fetch }) => {
// Run 20 requests with REQUESTS_PER_CONTRIVED_ERROR = '10' and
// record the results
const results1 = await Promise.all(
[
...Array.from({ length: expectedReqPerError - 1 }).map(() =>
fetch({ method: 'GET' })
),
fetch({ method: 'POST' }),
...Array.from({ length: expectedReqPerError - 1 }).map(() =>
fetch({ method: 'PUT' })
),
fetch({ method: 'DELETE' })
].map((p) => p.then((r) => r.status))
);
process.env.REQUESTS_PER_CONTRIVED_ERROR = '0';
// Run 10 requests with REQUESTS_PER_CONTRIVED_ERROR = '0' and record the
// results
const results2 = await Promise.all(
Array.from({ length: expectedReqPerError }).map(() =>
fetch().then((r) => r.status)
)
);
// We expect results1 to be an array with eighteen `200`s and two
// `555`s in any order
//
// https://github.com/jest-community/jest-extended#toincludesamemembersmembers
// because responses could be received out of order
expect(results1).toIncludeSameMembers([
...Array.from({ length: expectedReqPerError - 1 }).map(() => 200),
555,
...Array.from({ length: expectedReqPerError - 1 }).map(() => 200),
555
]);
// We expect results2 to be an array with ten `200`s
expect(results2).toStrictEqual([
...Array.from({ length: expectedReqPerError }).map(() => 200)
]);
}
});
});Further documentation can be found under docs/.
Since NTARH is meant for unit testing API routes rather than faithfully
recreating Next.js functionality, NTARH's feature set comes with some caveats.
Namely: no Next.js features will be available that are external to processing
API routes and executing their handlers. This includes middleware and
NextResponse.next (see requestPatcher if you need to mutate the
Request before it gets to the handler under test), metadata, static
assets, OpenTelemetry and instrumentation, caching,
styling, server actions and mutations, helper functions
(except: cookies, fetch (global), headers, NextRequest, NextResponse,
notFound, permanentRedirect, redirect, and userAgent), and anything
related to React or components.
NTARH is for testing your API route handlers only.
Further, any support NTARH appears to have for any "edge runtime" (or any
other runtime) beyond what is provided by AppRouteRouteModule is merely
cosmetic. Your tests will always run in Node.js (or your runner of choice)
and never in a different runtime, realm, or VM. This means unit testing like
with NTARH must be done in addition to, and not in lieu of, more holistic
testing practices (e.g. end-to-end).
If you're having trouble with your App Router and/or Edge Runtime routes, consider opening a new issue!
Also note that Next.js's middleware only supports the Edge runtime, even if the Next.js application is being run entirely by Node.js. This is an artificial constraint imposed by Next.js; when running the middleware locally (via
npm run devor something similar), the middleware will still run on Node.js.Next.js's middleware limitation is discussed at length here.
Next.js's current App Router implementation mutates the global fetch function,
redefining it entirely. This can cause problems in testing environments
where the global fetch is to be mocked by something else.
Internally, NTARH sidesteps this issue entirely by caching the value of
globalThis.fetch upon import. This also means NTARH completely sidesteps other
tools that rely on interception through rewriting the global fetch function,
such as Mock Service Worker (MSW). We still include the MSW bypass headers
with NTARH requests since we cannot guarantee that NTARH will not be imported
after MSW has finished patching global fetch.
Similarly, it is impossible for NTARH to meaningfully track mutations to the
global fetch function; NTARH cannot tell the difference between Next.js
overwriting fetch and, say, a Jest spy overwriting fetch. Therefore, NTARH
does not restore the cached fetch after the function returns.
If Next.js's patching of fetch is causing trouble for you, you can do what
NTARH does: capture the current global fetch (perhaps after setting up MSW)
and then restore it after each test:
const originalGlobalFetch = fetch;
afterEach(function () {
// Undo what Next.js does to the global fetch function
globalThis.fetch = originalGlobalFetch;
});AppRouteRouteModule and its dependents want AsyncLocalStorage to be
available globally and immediately. Unfortunately, Node.js does not place
AsyncLocalStorage in globalThis natively.
NTARH handles this by ensuring AsyncLocalStorage is added to globalThis
before Next.js needs it. This is why NTARH should always be the very first
import in any test file.
As of version 4.0.0, NTARH supports both the App Router (for next@>=14.0.4)
and the "legacy" Pages Router Next.js APIs. However, due to the code churn with
next@13, NTARH's support for the App Router begins at [email protected]. See
here and here for more information.
Additionally, as of version 2.1.0, NTARH's Pages Router support is fully
backwards compatible with Next.js going allll the way back to [email protected]
when API routes were first introduced!
If you're working with the Pages Router and next@<9.0.6 (so: before
next-server was merged into next), you might need to install
next-server manually:
npm install --save-dev next-serverSimilarly, if you are using npm@<7 or node@<15, you must install Next.js
and its peer dependencies manually. This is because npm@<7 does not install
peer dependencies by default.
npm install --save-dev next@latest reactIf you're also using an older version of Next.js, ensure you install the peer dependencies (like
react) that your specific Next.js version requires!
Note that jsdom does not support global fetch natively. This should not be an issue, however, since neither your API code nor your API test code should be executed in a browser-like environment.
For projects configured to use jsdom by default, you can use an annotation to switch environments only in the files housing your API tests:
/**
* @jest-environment node
*/
// ⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆
import { testApiHandler } from 'next-test-api-route-handler';
test('use the node test environment for all tests in this file', () => {
//...
});If you're dead set on using jsdom over the node testing environment with NTARH, see here and here for workarounds.
I'm constantly creating things with Next.js. Most of these applications have a major API component. Unfortunately, Next.js doesn't make unit testing your APIs very easy. After a while, I noticed some conventions forming around how I liked to test my APIs and NTARH was born 🙂
Of course, this all was back before the app router or edge routes existed. NTARH got app router and edge route support in version 4.
My hope is that NTARH gets obsoleted because Vercel provided developers with
some officially supported tooling/hooks for lightweight route execution where
handlers are passed fully initialized instances of
NextRequest/NextResponse/NextApiRequest/NextApiResponse without
ballooning the execution time of the tests. That is: no spinning up the entire
Next.js runtime just to run a single test in isolation.
It doesn't seem like it'd be such a lift to surface a wrapped version of the
Pages Router's apiResolver function and a pared-down subclass of the App
Router's AppRouteRouteModule, both accessible with something like
import { ... } from 'next/test'. This is essentially what NTARH does.
This is a CJS2 package with statically-analyzable exports
built by Babel for Node.js versions that are not end-of-life. For TypeScript
users, this package supports both "Node10" and "Node16" module resolution
strategies.
Expand details
That means both CJS2 (via require(...)) and ESM (via import { ... } from ...
or await import(...)) source will load this package from the same entry points
when using Node. This has several benefits, the foremost being: less code
shipped/smaller package size, avoiding dual package
hazard entirely, distributables are not
packed/bundled/uglified, a drastically less complex build process, and CJS
consumers aren't shafted.
Each entry point (i.e. ENTRY) in package.json's
exports[ENTRY] object includes one or more export
conditions. These entries may or may not include: an
exports[ENTRY].types condition pointing to a type
declarations file for TypeScript and IDEs, an
exports[ENTRY].module condition pointing to
(usually ESM) source for Webpack/Rollup, an exports[ENTRY].node condition
pointing to (usually CJS2) source for Node.js require and import, an
exports[ENTRY].default condition pointing to source for browsers and other
environments, and other conditions not enumerated
here. Check the package.json file to see which export
conditions are supported.
Though package.json includes
{ "type": "commonjs" }, note that any ESM-only entry points will
be ES module (.mjs) files. Finally, package.json also
includes the sideEffects key, which is false for
optimal tree shaking where appropriate.
See LICENSE.
New issues and pull requests are always welcome and greatly appreciated! 🤩 Just as well, you can star 🌟 this project to let me know you found it useful! ✊🏿 Or you could buy me a beer 🥺 Thank you!
See CONTRIBUTING.md and SUPPORT.md for more information.
Thanks goes to these wonderful people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
![dependabot[bot] avatar](https://avatars.githubusercontent.com/in/29110?v=4 "dependabot[bot]")
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