msw-expect
MSW works great to mock responses in unit tests, but it’s missing a way to assert on what requests are made like nock
can. Well, now you can too with msw-expect
and Jest!
And it works with TypeScript!
Install
You’ll want to install msw
as well, if you haven’t already.
or
Use
For simplest setup with our built-in MSW server, in your jest.config.js
:
module.exports = {
setupFilesAfterEnv: ["msw-expect/setup"],
};
In your test, you can wrap your MSW handlers with mockHandler
:
import { rest } from "msw";
import { mockHandler, server } from "msw-expect";
import { myMswHandler } from "./myMswHandler";
import { fetchFlavor } from "./fetchFlavor";
test("fetch flavor called with flavor param", async () => {
const handler = mockHandler(myMswHandler);
server.use(
rest.get(
"https://api.example.com/flavors",
// Only use the "as..." part if you're using TypeScript.
handler as typeof myMswHandler
)
);
await fetchFlavor();
expect(handler.getRequest()).toMatchObject({
searchParams: {
flavor: "cherry",
},
});
});
Or, if you don’t need to mock the response, you don’t need to provide a handler to wrap (the default just responds with 200):
// Only import `DefaultResponseResolver` if you're using TypeScript.
import { DefaultResponseResolver } from "msw-expect";
const handler = mockHandler();
server.use(
rest.post(
"https://api.example.com/flavors",
// Only use the "as..." part if you're using TypeScript.
handler as DefaultResponseResolver
)
);
You can also assert on request URL, body, headers, etc., with getRequest()
as well as response status, body, etc., with getResponse()
:
server.use(
rest.post(
"https://api.example.com/flavors",
// Only use the "as..." part if you're using TypeScript.
handler as typeof myMswHandler
)
);
await postFlavor();
expect(handler.getRequest()).toMatchObject({
url: "https://api.example.com/flavors",
headers: {
"x-api-key": "123",
},
body: {
flavor: "cherry",
},
});
expect(handler.getResponse()).toMatchObject({
status: 200,
body: {
flavor: "cherry",
},
});
You can use any of the Jest assertion utilities, including deeply nested expect.stringMatching(regex)
, expect.arrayContaining(array)
, etc.
To assert multiple requests and responses, use getRequest(index)
and getResponse(index)
:
// Assert on the 2nd request (1st index):
expect(handler.getRequest(1)).toMatchObject({
searchParams: {
flavor: "imaginary",
},
});
// Assert on the 3rd response (2nd index):
expect(handler.getResponse(2)).toMatchObject({
status: 404,
});
To assert count of requests, use getRequests()
:
expect(handler.getRequests()).toHaveLength(3);
Reset request/response arrays between tests
If you want to clear the request/response arrays between tests, use the reset
method:
describe('test', () => {
beforeEach(() => {
handler.reset()
});
})
Manual Server
If you prefer to configure your server manually, you do not need to use msw-expect/setup
in your Jest config.
Instead, you can configure a vanilla MSW server yourself:
import { setupServer } from "msw/node";
export const server = setupServer();