Trying to unit test your Next.js API route handlers? Want to avoid mucking around with custom servers and writing boring test infra just to get some unit tests working? Want your handlers to receive actual NextApiRequest and NextApiResponse objects rather than having to hack something together with express? Then look no further! 🤩 This package allows you to quickly test your Next.js API routes/handlers in an isolated Next.js-like context.
next-test-api-route-handler uses Next.js's internal API resolver to precisely
emulate API route handling. To guarantee stability, this package is
automatically tested against each release of Next.js. Go forth and test
confidently!
✨
✨
Looking for a version of this package compatible with an earlier major release of Next.js? Breaking changes are documented in CHANGELOG.md.
Note: NPM versions >=7 may need
npm install --legacy-peer-depsuntil upstream peer dependency problems are resolved.
npm install --save-dev next-test-api-route-handler[additional details]
Note: typical users don't need to read through this! This information is primarily useful for those attempting to bundle this package or for those who have an opinion on ESM versus CJS.
This is a dual CJS2/ES module package. That means this package exposes both CJS2 and ESM entry points.
Loading this package via require(...) will cause Node to use the CJS2
bundle entry point, disable tree shaking in Webpack 4,
and lead to larger bundles in Webpack 5. Alternatively, loading this package via
import { ... } from ... or import(...) will cause Node to use the ESM entry
point in versions that support it and in Webpack. Using the
import syntax is the modern, preferred choice.
For backwards compatibility with Webpack 4 and Node versions < 14,
package.json retains the module key, which
points to the ESM entry point, and the main key, which
points to both the ESM and CJS2 entry points implicitly (no file extension). For
Webpack 5 and Node versions >= 14, package.json includes the
exports key, which points to both entry points explicitly.
Though package.json includes
{ "type": "commonjs"}, note that the ESM entry points are ES
module (.mjs) files. package.json also includes the
sideEffects key, which is false for optimal tree
shaking, and the types key, which points to a TypeScript
declarations file.
Additionally, this package does not maintain shared state and so does not exhibit the dual package hazard.
// ESM
import { testApiHandler } from 'next-test-api-route-handler'// CJS
const { testApiHandler } = require('next-test-api-route-handler');Quick start:
// File: test/unit.test.js
import * as endpoint from '../pages/api/your-endpoint'
import { testApiHandler } from 'next-test-api-route-handler'
import type { WithConfig } from '@ergodark/next-types'
// Import the handler under test from the pages/api directory and respect the
// Next.js config object if it's exported
const endpoint: WithConfig<typeof Endpoint.default> = Endpoint.default;
endpoint.config = Endpoint.config;
await testApiHandler({
requestPatcher: req => req.headers = { key: SPECIAL_API_KEY },
handler: endpoint,
test: async ({ fetch }) => {
expect(await fetch({ method: 'GET', body: 'data' })).toStrictEqual({ json: 'response' });
}
});The interface for testApiHandler looks like this:
async function testApiHandler({ requestPatcher, responsePatcher, params, handler, test }: {
requestPatcher?: (req: IncomingMessage) => void,
responsePatcher?: (res: ServerResponse) => void,
params?: Record<string, unknown>,
handler: (req: NextApiRequest, res: NextApiResponse) => Promise<void>
test: (obj: { fetch: (init?: RequestInit) => ReturnType<typeof fetch> }) => Promise<void>,
})requestPatcher is a function that receives an IncomingMessage. Use this
function to modify the request before it's injected into Next.js's resolver.
responsePatcher is a function that receives a ServerResponse. Use this
function to modify the response before it's injected into Next.js's resolver.
params is an object representing "processed" dynamic routes, e.g. testing a
handler that expects /api/user/:id requires params: { id: ... }. This should
not be confused with requiring query string parameters, which are parsed out
from the url and added to the params object automatically.
handler is 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.
test is a function that returns a promise (or async) where test assertions can
be run. This function receives one parameter: fetch, which is a simple
unfetch instance (note that the url parameter, i.e. the first parameter
in fetch(...), is omitted). Use this to send HTTP requests to the
handler under test.
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?
import * as UnreliableHandler from '../pages/api/unreliable'
import { testApiHandler } from 'next-test-api-route-handler'
import { shuffle } from 'fast-shuffle'
import array from 'array-range'
import type { WithConfig } from '@ergodark/next-types'
// Import the handler under test from the pages/api directory and respect the
// Next.js config object if it's exported
const unreliableHandler: WithConfig<typeof UnreliableHandler.default> = UnreliableHandler.default;
unreliableHandler.config = UnreliableHandler.config;
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 = '10';
const expectedReqPerError = parseInt(process.env.REQUESTS_PER_CONTRIVED_ERROR);
// Returns one of ['GET', 'POST', 'PUT', 'DELETE'] at random
const getMethod = () => shuffle(['GET', 'POST', 'PUT', 'DELETE'])[0];
// Returns the status code from a response object
const getStatus = async (res: Promise<Response>) => (await res).status;
await testApiHandler({
handler: unreliableHandler,
test: async ({ fetch }) => {
// Run 20 requests with REQUESTS_PER_CONTRIVED_ERROR = '10' and
// record the results
const results1 = await Promise.all([
...array(expectedReqPerError - 1).map(_ => getStatus(fetch({ method: getMethod() }))),
getStatus(fetch({ method: getMethod() })),
...array(expectedReqPerError - 1).map(_ => getStatus(fetch({ method: getMethod() }))),
getStatus(fetch({ method: getMethod() }))
].map(p => p.then(s => s, _ => null)));
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(expectedReqPerError).map(_ => getStatus(fetch({ method: getMethod() }))),
].map(p => p.then(s => s, _ => null)));
// 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(expectedReqPerError - 1).map(_ => 200),
555,
...array(expectedReqPerError - 1).map(_ => 200),
555
]);
// We expect results2 to be an array with ten `200`s
expect(results2).toStrictEqual([
...array(expectedReqPerError).map(_ => 200),
]);
}
});
});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?
import * as V3FlightsSearchHandler from '../pages/api/v3/flights/search'
import { testApiHandler } from 'next-test-api-route-handler'
import { DUMMY_API_KEY as KEY, getFlightData, RESULT_SIZE } from '../backend'
import array from 'array-range'
import type { WithConfig } from '@ergodark/next-types'
// Import the handler under test from the pages/api directory and respect the
// Next.js config object if it's exported
const v3FlightsSearchHandler: WithConfig<typeof V3FlightsSearchHandler.default> = V3FlightsSearchHandler.default;
v3FlightsSearchHandler.config = V3FlightsSearchHandler.config;
it('returns expected public flights with respect to match', async () => {
expect.hasAssertions();
// Get the flight data currently in the test database
const flights = 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 automatically, though we
// also could have used `params` or `fetch({ ... })` itself instead.
//
// Example URI for `https://google.com/search?params=yes` would be
// `/search?params=yes`
const genUrl = function*() {
yield `/?match=${encode({ airline: 'Spirit' })}`; // i.e. we want all the flights matching Spirit airlines!
yield `/?match=${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: { $lte: 500 }})}`;
}();
await testApiHandler({
// Patch the request object to include our dummy URI
requestPatcher: req => {
req.url = genUrl.next().value || undefined;
// Could have done this instead of fetch({ headers: { KEY }}) below:
// req.headers = { KEY };
},
handler: v3FlightsSearchHandler,
test: async ({ fetch }) => {
// 8 URLS from genUrl means 8 calls to fetch:
const responses = await Promise.all(array(8).map(_ => {
return fetch({ headers: { KEY }}).then(r => r.ok ? r.json() : r.status);
}));
// We expect all of the responses to be 200
expect(responses.some(o => !o?.success)).toBe(false);
// We expect the array of flights returned to match our
// expectations given we already know what dummy data will be
// returned:
// https://github.com/jest-community/jest-extended#toincludesamemembersmembers
// because responses could be received out of order
expect(responses.map(r => r.flights)).toIncludeSameMembers([
flights.filter(f => f.airline == 'Spirit').slice(0, RESULT_SIZE),
flights.filter(f => f.type == 'departure').slice(0, RESULT_SIZE),
flights.filter(f => f.landingAt == 'F1A').slice(0, RESULT_SIZE),
flights.filter(f => f.seatPrice == 500).slice(0, RESULT_SIZE),
flights.filter(f => f.seatPrice > 500).slice(0, RESULT_SIZE),
flights.filter(f => f.seatPrice >= 500).slice(0, RESULT_SIZE),
flights.filter(f => f.seatPrice < 500).slice(0, RESULT_SIZE),
flights.filter(f => f.seatPrice <= 500).slice(0, RESULT_SIZE),
]);
}
});
// We expect these two to fail with 400 errors
await testApiHandler({
handler: v3FlightsSearchHandler,
requestPatcher: req => { req.url = `/?match=${encode({ ffms: { $eq: 500 }})}` },
test: async ({ fetch }) => expect((await fetch({ headers: { KEY }})).status).toBe(400)
});
await testApiHandler({
handler: v3FlightsSearchHandler,
requestPatcher: req => { req.url = `/?match=${encode({ bad: 500 })}` },
test: async ({ fetch }) => expect((await fetch({ headers: { KEY }})).status).toBe(400)
});
});Check out the tests for more examples.
Project documentation can be found under docs/.
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! ✊🏿 Thank you!
See CONTRIBUTING.md and SUPPORT.md for more information.