Vitest Fetch Mock

!Node.js CI

This project was forked from jest-fetch-mock, and tweaked slightly to run
with Vitest instead of Jest. It is mostly compatible with jest-fetch-mock, with the main difference being that you
need to create fetchMock with a function call, and provide vi to it, rather than relying on a global vi or (jest
in jest-fetch-mock's case). See Usage for more details.

Fetch is the canonical way to do HTTP requests in the browser and other modern runtimes. Vitest Fetch Mock allows you to
easily mock your fetch calls and return the response you need to fake the HTTP requests. It's easy to setup and you
don't need a library like nock to get going and it uses Vitest's built-in support for mocking under the surface. This
means that any of the vi.fn() methods are also available. For more information on the Vitest mock API, check their
docs here

As of version 0.4.0, vitest-fetch-mock mocks the global
Fetch method, which is present in all modern runtimes
and browsers. Previous versions used a fetch polyfill to run in older versions of Node.js. See
Compatibility for details.

Contents

- Usage
- Compatibility
- Package Installation
- Setup for all tests
- Setup for an individual test
- API
- Examples
- Simple mock and assert
- Mocking all fetches
- Mocking a failed fetch
- Mocking multiple fetches with different responses
- Mocking multiple fetches with fetch.mockResponses
- Reset mocks between tests with fetch.resetMocks
- Using fetch.mock to inspect the mock state of each fetch call
- Using functions to mock slow servers

Usage

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The most recent versions of vitest-fetch-mock support Vitest 2 and Node.js 18 and above. If you are using Vitest version
1.x or an older version of node, please install vitest-fetch-mock0.2.2.

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To setup your fetch mock you need to do the following things:

``
$ npm install --save-dev vitest-fetch-mock
`

Create a setupVitest file to setup the mock or add this to an existing setupFile. :

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`js
//setupVitest.js or similar file
import createFetchMock from 'vitest-fetch-mock';
import { vi } from 'vitest';

const fetchMocker = createFetchMock(vi);

// sets globalThis.fetch and globalThis.fetchMock to our mocked version
fetchMocker.enableMocks();
`

Add the setup file to your vitest config:

`JSON
"test": {
"setupFiles": [
"./setupVitest.js"
]
}
`

With this done, you'll have fetch and fetchMock available on the global scope. Fetch will be used as usual by your
code and you'll use fetchMock in your tests

#### Default not mocked

If you would like to have the 'fetchMock' available in all tests but not enabled then add fetchMock.dontMock() after
the ...enableMocks() line in setupVitest.js:

`js
import createFetchMock from 'vitest-fetch-mock';
import { vi } from 'vitest';
const fetchMocker = createFetchMock(vi);

// adds the 'fetchMock' global variable and rewires 'fetch' global to call 'fetchMock' instead of the real implementation
fetchMocker.enableMocks();

// changes default behavior of fetchMock to use the real 'fetch' implementation and not mock responses
fetchMocker.dontMock();
`

If you want a single test file to return to the default behavior of mocking all responses, add the following to the test
file:

`js
beforeEach(() => {
// if you have an existing beforeEach just add the following line to it
fetchMocker.doMock();
});
`

To enable mocking for a specific URL only:

`js
beforeEach(() => {
// if you have an existing beforeEach just add the following lines to it
fetchMocker.mockIf(/^https?:\/\/example.com.*$/, (req) => {
if (req.url.endsWith('/path1')) {
return 'some response body';
} else if (req.url.endsWith('/path2')) {
return {
body: 'another response body',
headers: {
'X-Some-Response-Header': 'Some header value',
},
};
} else {
return {
status: 404,
body: 'Not Found',
};
}
});
});
`

If you have changed the default behavior to use the real implementation, you can guarantee the next call to fetch will
be mocked by using the mockOnce function:

`js
fetchMocker.mockOnce('the next call to fetch will always return this as the body');
`

This function behaves exactly like fetchMocker.once but guarantees the next call to fetch will be mocked even if the
default behavior of fetchMock is to use the real implementation. You can safely convert all you fetchMocker.once calls
to fetchMocker.mockOnce without a risk of changing their behavior.

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Add the following line to the start of your test case (before any other imports)

`js
import createFetchMock from 'vitest-fetch-mock';
import { vi } from 'vitest';

const fetchMocker = createFetchMock(vi);
fetchMocker.enableMocks();
`

#### TypeScript importing

If you are using TypeScript and receive errors about the fetchMock global not existing, add a global.d.ts file to
the root of your project (or add the following line to an existing global file):

`typescript
import 'vitest-fetch-mock';
`

API

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- fetch.mockResponse(bodyOrFunction, init): fetch - Mock all fetch calls
- fetch.mockResponseOnce(bodyOrFunction, init): fetch - Mock each fetch call independently
- fetch.once(bodyOrFunction, init): fetch - Alias for mockResponseOnce(bodyOrFunction, init)
- fetch.mockResponses(...responses): fetch - Mock multiple fetch calls independently
- Each argument is an array taking [bodyOrFunction, init]
- fetch.mockReject(errorOrFunction): fetch - Mock all fetch calls, letting them fail directly
- fetch.mockRejectOnce(errorOrFunction): fetch - Let the next fetch call fail directly
- fetch.mockAbort(): fetch - Causes all fetch calls to reject with an "Aborted!" error
- fetch.mockAbortOnce(): fetch - Causes the next fetch call to reject with an "Aborted!" error

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Instead of passing body, it is also possible to pass a function that returns a promise. The promise should resolve with
a string or an object containing body and init props

i.e:

`js
fetch.mockResponse(() => callMyApi().then((res) => ({ body: 'ok' })));
// OR
fetch.mockResponse(() => callMyApi().then((res) => 'ok'));
`

The function may take an optional "request" parameter of type http.Request:

`js
fetch.mockResponse((req) =>
req.url === 'http://myapi/' ? callMyApi().then((res) => 'ok') : Promise.reject(new Error('bad url'))
);
`

Note: the request "url" is parsed and then printed using the equivalent of new URL(input).href so it may not match
exactly with the URL's passed to fetch if they are not fully qualified. For example, passing "http://foo.com" to
fetch will result in the request URL being "http://foo.com/" (note the trailing slash).

The same goes for rejects:

`js
fetch.mockReject(() => doMyAsyncJob().then((res) => Promise.reject(res.errorToRaise)));
// OR
fetch.mockReject((req) =>
req.headers.get('content-type') === 'text/plain'
? Promise.reject('invalid content type')
: doMyAsyncJob().then((res) => Promise.reject(res.errorToRaise))
);
`

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- fetch.resetMocks() - Clear previously set mocks so they do not bleed into other mocks
- fetch.enableMocks() - Enable fetch mocking by overriding global.fetch and mocking node-fetch
- fetch.disableMocks() - Disable fetch mocking and restore default implementation of fetch and/or node-fetch
- fetch.mock - The mock state for your fetch calls. Make assertions on the arguments given to fetch when called by
the functions you are testing. For more information check the
vitest docs

For information on the arguments body and init can take, you can look at the MDN docs on the Response Constructor
function, which vitest-fetch-mock uses under the surface.

https://developer.mozilla.org/en-US/docs/Web/API/Response/Response

Each mocked response or err or will return a MockInstance Function. You can use
methods like .toHaveBeenCalledWith to ensure that the mock function was called with specific arguments. For more
methods detail, take a look at this.

Examples

In most of the complicated examples below, I am testing my action creators in Redux, but it doesn't have to be used with
Redux.

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In this simple example I won't be using any libraries. It is a simple fetch request, in this case to google.com. First
we setup the beforeEach callback to reset our mocks. This isn't strictly necessary in this example, but since we will
probably be mocking fetch more than once, we need to reset it across our tests to assert on the arguments given to
fetch. Make sure the function wrapping your test is marked as async.

Once we've done that we can start to mock our response. We want to give it an object with a data property and a string
value of 12345 and wrap it in JSON.stringify to JSONify it. Here we use mockResponseOnce, but we could also use
once, which is an alias for a call to mockResponseOnce.

We then call the function that we want to test with the arguments we want to test with. We use await to wait until the
response resolves, and then assert we have got the correct data back.

Finally we can assert on the .mock state that Vitest provides for us to test what arguments were given to fetch and
how many times it was called

`js
//api.js
export function APIRequest(who) {
if (who === 'google') {
return fetch('https://google.com').then((res) => res.json());
} else {
return 'no argument provided';
}
}
`

`js
//api.test.js
import { APIRequest } from './api';

describe('testing api', () => {
beforeEach(() => {
fetch.resetMocks();
});

it('calls google and returns data to me', async () => {
fetch.mockResponseOnce(JSON.stringify({ data: '12345' }));

//assert on the response
const res = await APIRequest('google');
expect(res.data).toEqual('12345');

//assert on the times called and arguments given to fetch
expect(fetch.requests().length).toEqual(1);
expect(fetch.requests()[0].url).toEqual('https://google.com/');
});
});
`

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In this example I am mocking just one fetch call. Any additional fetch calls in the same function will also have the
same mock response. For more complicated functions with multiple fetch calls, you can check out example 3.

`js
import configureMockStore from 'redux-mock-store'; // mock store
import thunk from 'redux-thunk';

const middlewares = [thunk];
const mockStore = configureMockStore(middlewares);

import { getAccessToken } from './accessToken';

describe('Access token action creators', () => {
it('dispatches the correct actions on successful fetch request', () => {
fetch.mockResponse(JSON.stringify({ access_token: '12345' }));

const expectedActions = [{ type: 'SET_ACCESS_TOKEN', token: { access_token: '12345' } }];
const store = mockStore({ config: { token: '' } });

return (
store
.dispatch(getAccessToken())
//getAccessToken contains the fetch call
.then(() => {
// return of async actions
expect(store.getActions()).toEqual(expectedActions);
})
);
});
});
`

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In this example I am mocking just one fetch call but this time using the mockReject function to simulate a failed
request. Any additional fetch calls in the same function will also have the same mock response. For more complicated
functions with multiple fetch calls, you can check out example 3.

`js
import configureMockStore from 'redux-mock-store'; // mock store
import thunk from 'redux-thunk';

const middlewares = [thunk];
const mockStore = configureMockStore(middlewares);

import { getAccessToken } from './accessToken';

describe('Access token action creators', () => {
it('dispatches the correct actions on a failed fetch request', () => {
fetch.mockReject(new Error('fake error message'));

const expectedActions = [{ type: 'SET_ACCESS_TOKEN_FAILED', error: { status: 503 } }];
const store = mockStore({ config: { token: '' } });

return (
store
.dispatch(getAccessToken())
//getAccessToken contains the fetch call
.then(() => {
// return of async actions
expect(store.getActions()).toEqual(expectedActions);
})
);
});
});
`

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Fetches can be mocked to act as if they were aborted during the request. This can be done in 4 ways:



1. Using fetch.mockAborted()


2. Using fetch.mockAbortedOnce()


3. Passing a request (or request init) with a 'signal' to fetch that has been aborted


4. Passing a request (or request init) with a 'signal' to fetch and a async function to fetch.mockResponse or fetch.mockResponseOnce that causes the signal to abort before returning the response



`js
describe('Mocking aborts', () => {
beforeEach(() => {
fetch.resetMocks();
fetch.doMock();
vi.useFakeTimers();
});
afterEach(() => {
vi.useRealTimers();
});

it('rejects with an Aborted! Error', () => {
fetch.mockAbort();
expect(fetch('/')).rejects.toThrow('Aborted!');
});
it('rejects with an Aborted! Error once then mocks with empty response', async () => {
fetch.mockAbortOnce();
await expect(fetch('/')).rejects.toThrow('Aborted!');
await expect(request()).resolves.toEqual('');
});

it('throws when passed an already aborted abort signal', () => {
const c = new AbortController();
c.abort();
expect(() => fetch('/', { signal: c.signal })).toThrow('Aborted!');
});

it('rejects when aborted before resolved', async () => {
const c = new AbortController();
fetch.mockResponse(async () => {
vi.advanceTimersByTime(60);
return '';
});
setTimeout(() => c.abort(), 50);
await expect(fetch('/', { signal: c.signal })).rejects.toThrow('Aborted!');
});
});
`

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Set the counter option >= 1 in the response init object to mock a redirected response
https://developer.mozilla.org/en-US/docs/Web/API/Response/redirected. Note, this will only work in Node.js as it's a
feature of node fetch's response class https://github.com/node-fetch/node-fetch/blob/master/src/response.js#L39.

`js
fetchMock.mockResponse('

', {
counter: 1,
status: 200,
statusText: 'ok',
});
`

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In this next example, the store does not yet have a token, so we make a request to get an access token first. This means
that we need to mock two different responses, one for each of the fetches. Here we can use fetch.mockResponseOnce or
fetch.once to mock the response only once and call it twice. Because we return the mocked function, we can chain this
jQuery style. It internally uses Vitest's mockImplementationOnce. You can read more about it on the
Vitest documentation

`js
import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';

const middlewares = [thunk];
const mockStore = configureMockStore(middlewares);

import { getAnimeDetails } from './animeDetails';

describe('Anime details action creators', () => {
it('dispatches requests for an access token before requesting for animeDetails', () => {
fetch.once(JSON.stringify({ access_token: '12345' })).once(JSON.stringify({ name: 'naruto' }));

const expectedActions = [
{ type: 'SET_ACCESS_TOKEN', token: { access_token: '12345' } },
{ type: 'SET_ANIME_DETAILS', animeDetails: { name: 'naruto' } },
];
const store = mockStore({ config: { token: null } });

return (
store
.dispatch(getAnimeDetails('21049'))
//getAnimeDetails contains the 2 fetch calls
.then(() => {
// return of async actions
expect(store.getActions()).toEqual(expectedActions);
})
);
});
});
`

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fetch.mockResponses takes as many arguments as you give it, all of which are arrays representing each Response Object.
It will then call the mockImplementationOnce for each response object you give it. This reduces the amount of
boilerplate code you need to write. An alternative is to use .once and chain it multiple times if you don't like
wrapping each response arguments in a tuple/array.

In this example our actionCreator calls fetch 4 times, once for each season of the year and then concatenates the
results into one final array. You'd have to write fetch.mockResponseOnce 4 times to achieve the same thing:

`js
describe('getYear action creator', () => {
it('dispatches the correct actions on successful getSeason fetch request', () => {
fetch.mockResponses(
[JSON.stringify([{ name: 'naruto', average_score: 79 }]), { status: 200 }],
[JSON.stringify([{ name: 'bleach', average_score: 68 }]), { status: 200 }],
[JSON.stringify([{ name: 'one piece', average_score: 80 }]), { status: 200 }],
[JSON.stringify([{ name: 'shingeki', average_score: 91 }]), { status: 200 }]
);

const expectedActions = [
{
type: 'FETCH_ANIMELIST_REQUEST',
},
{
type: 'SET_YEAR',
payload: {
animes: [
{ name: 'naruto', average_score: 7.9 },
{ name: 'bleach', average_score: 6.8 },
{ name: 'one piece', average_score: 8 },
{ name: 'shingeki', average_score: 9.1 },
],
year: 2016,
},
},
{
type: 'FETCH_ANIMELIST_COMPLETE',
},
];
const store = mockStore({
config: {
token: { access_token: 'wtw45CmyEuh4P621IDVxWkgVr5QwTg3wXEc4Z7Cv' },
},
years: [],
});

return (
store
.dispatch(getYear(2016))
//This calls fetch 4 times, once for each season
.then(() => {
// return of async actions
expect(store.getActions()).toEqual(expectedActions);
})
);
});
});
`

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fetch.resetMocks resets the fetch mock to give fresh mock data in between tests. It only resets the fetch calls as
to not disturb any other mocked functionality.

`js
describe('getYear action creator', () => {
beforeEach(() => {
fetch.resetMocks();
});
it('dispatches the correct actions on successful getSeason fetch request', () => {

fetch.mockResponses(
[
JSON.stringify([ {name: 'naruto', average_score: 79} ]), { status: 200}
],
[
JSON.stringify([ {name: 'bleach', average_score: 68} ]), { status: 200}
]
)

const expectedActions = [
{
type: 'FETCH_ANIMELIST_REQUEST'
},
{
type: 'SET_YEAR',
payload: {
animes: [
{name: 'naruto', average_score: 7.9},
{name: 'bleach', average_score: 6.8}
],
year: 2016,
}
},
{
type: 'FETCH_ANIMELIST_COMPLETE'
}
]
const store = mockStore({
config: { token: { access_token: 'wtw45CmyEuh4P621IDVxWkgVr5QwTg3wXEc4Z7Cv' }},
years: []
})

return store.dispatch(getYear(2016))
//This calls fetch 2 times, once for each season
.then(() => { // return of async actions
expect(store.getActions()).toEqual(expectedActions)
})
});
it('dispatches the correct actions on successful getSeason fetch request', () => {

fetch.mockResponses(
[
JSON.stringify([ {name: 'bleach', average_score: 68} ]), { status: 200}
],
[
JSON.stringify([ {name: 'one piece', average_score: 80} ]), { status: 200}
],
[
JSON.stringify([ {name: 'shingeki', average_score: 91} ]), { status: 200}
]
)

const expectedActions = [
{
type: 'FETCH_ANIMELIST_REQUEST'
},
{
type: 'SET_YEAR',
payload: {
animes: [
{name: 'bleach', average_score: 6.8},
{name: 'one piece', average_score: 8},
{name: 'shingeki', average_score: 9.1}
],
year: 2016,
}
},
{
type: 'FETCH_ANIMELIST_COMPLETE'
}
]
const store = mockStore({
config: { token: { access_token: 'wtw45CmyEuh4P621IDVxWkgVr5QwTg3wXEc4Z7Cv' }},
years: []
})

return store.dispatch(getYear(2016))
//This calls fetch 3 times, once for each season
.then(() => { // return of async actions
expect(store.getActions()).toEqual(expectedActions)
})
,

})
})
`

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fetch.mock by default uses Vitest's mocking functions. Therefore you can make
assertions on the mock state. In this example we have an arbitrary function that makes a different fetch request based
on the argument you pass to it. In our test, we run Vitest's beforeEach() and make sure to reset our mock before each
it() block as we will make assertions on the arguments we are passing to fetch(). Then we use the fetch.requests()
function to give us a history of all non-aborted requests (normalized) that were made. It can give you information on
each call, and their arguments which you can use for your expect() calls. Vitest also comes with some nice aliases for
the most used ones.

`js
// api.js

export function APIRequest(who) {
if (who === 'facebook') {
return fetch('https://facebook.com');
} else if (who === 'twitter') {
return fetch('https://twitter.com');
} else {
return fetch('https://google.com');
}
}
`

`js
// api.test.js
import { APIRequest } from './api';

describe('testing api', () => {
beforeEach(() => {
fetch.resetMocks();
});

it('calls google by default', () => {
fetch.mockResponse(JSON.stringify({ secret_data: '12345' }));
APIRequest();

// there was one request, which was not aborted
expect(fetch.requests().length).toEqual(1);
expect(fetch.requests()[0].url).toEqual('https://google.com/');
});

it('calls facebook', () => {
fetch.mockResponse(JSON.stringify({ secret_data: '12345' }));
APIRequest('facebook');

expect(fetch.requests().length).toEqual(2);
expect(fetch.requests()[0].url).toEqual('https://facebook.com/someOtherResource');
expect(fetch.requests()[1].url).toEqual('https://facebook.com/');
});

it('calls twitter', () => {
fetch.mockResponse(JSON.stringify({ secret_data: '12345' }));
APIRequest('twitter');

expect(fetch).toBeCalled(); // alias for expect(fetch.mock.calls.length).toEqual(1);
expect(fetch.requests().map((v) => v.url)).toContain('https://twitter.com/');
});
});
`

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By default you will want to have your fetch mock return immediately. However if you have some custom logic that needs to
tests for slower servers, you can do this by passing it a function and returning a promise when your function resolves

`js
// api.test.js
import { request } from './api';

describe('testing timeouts', () => {
it('resolves with function and timeout', async () => {
fetch.mockResponseOnce(() => new Promise((resolve) => setTimeout(() => resolve({ body: 'ok' }), 100)));
try {
const response = await request();
expect(response).toEqual('ok');
} catch (e) {
throw e;
}
});
});
`

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In some test scenarios, you may want to temporarily disable (or enable) mocking for all requests or the next (or a
certain number of) request(s). You may want to only mock fetch requests to some URLs that match a given request path
while in others you may want to mock all requests except those matching a given request path. You may even want to
conditionally mock based on request headers.

The conditional mock functions cause vitest-fetch-mock to pass fetches through to the concrete fetch implementation
conditionally. Calling fetch.dontMock, fetch.doMock, fetch.doMockIf or fetch.dontMockIf overrides the default
behavior of mocking/not mocking all requests. fetch.dontMockOnce, fetch.doMockOnce, fetch.doMockOnceIf and
fetch.dontMockOnceIf only overrides the behavior for the next call to fetch, then returns to the default behavior
(either mocking all requests or mocking the requests based on the last call to fetch.dontMock, fetch.doMock,
fetch.doMockIf and fetch.dontMockIf).

Calling fetch.resetMocks() will return to the default behavior of mocking all fetches with a text response of empty
string.

- fetch.dontMock() - Change the default behavior to not mock any fetches until fetch.resetMocks() or
fetch.doMock() is called
- fetch.doMock(bodyOrFunction?, responseInit?) - Reverses fetch.dontMock(). This is the default state after
fetch.resetMocks()
- fetch.dontMockOnce() - For the next fetch, do not mock then return to the default behavior for subsequent fetches.
Can be chained.
- fetch.doMockOnce(bodyOrFunction?, responseInit?) or fetch.mockOnce - For the next fetch, mock the response then
return to the default behavior for subsequent fetches. Can be chained.
- fetch.doMockIf(urlOrPredicate, bodyOrFunction?, responseInit?):fetch or fetch.mockIf - causes all fetches to be
not be mocked unless they match the given string/RegExp/predicate (i.e. "only mock 'fetch' if the request is for the
given URL otherwise, use the real fetch implementation")
- fetch.dontMockIf(urlOrPredicate, bodyOrFunction?, responseInit?):fetch - causes all fetches to be mocked unless they
match the given string/RegExp/predicate (i.e. "don't mock 'fetch' if the request is for the given URL, otherwise mock
the request")
- fetch.doMockOnceIf(urlOrPredicate, bodyOrFunction?, responseInit?):fetch or fetch.mockOnceIf - causes the next
fetch to be mocked if it matches the given string/RegExp/predicate. Can be chained. (i.e. "only mock 'fetch' if the
next request is for the given URL otherwise, use the default behavior")
- fetch.dontMockOnceIf(urlOrPredicate):fetch - causes the next fetch to be not be mocked if it matches the given
string/RegExp/predicate. Can be chained. (i.e. "don't mock 'fetch' if the next request is for the given URL, otherwise
use the default behavior")
- fetch.isMocking(input, init):boolean - test utility function to see if the given url/request would be mocked. This
is not a read only operation and any "MockOnce" will evaluate (and return to the default behavior)

For convenience, all the conditional mocking functions also accept optional parameters after the 1st parameter that call
mockResponse or mockResponseOnce respectively. This allows you to conditionally mock a response in a single call.

#### Conditional Mocking examples

`js
vi.mock('fetch', async () => {
const fetchActual = globalThis.fetch;
const mocked = {};
for (const key of Object.keys(fetchActual)) {
if (typeof fetchActual[key] === 'function') {
mocked[key] = vi.fn(fetchActual[key]);
} else {
mocked[key] = fetchActual[key];
}
}
return mocked;
})

describe('conditional mocking', () => {
const realResponse = 'REAL FETCH RESPONSE'
const mockedDefaultResponse = 'MOCKED DEFAULT RESPONSE'
const testUrl = defaultRequestUri
let fetchSpy
beforeEach(() => {
fetch.resetMocks()
fetch.mockResponse(mockedDefaultResponse)
vi.mocked(fetch)
.mockImplementation(async () =>
Promise.resolve(new Response(realResponse))
)
})

afterEach(() => {
vi.mocked(fetch).mockRestore()
})

const expectMocked = async (uri, response = mockedDefaultResponse) => {
return expect(request(uri)).resolves.toEqual(response)
}
const expectUnmocked = async uri => {
return expect(request(uri)).resolves.toEqual(realResponse)
}

describe('once', () => {
it('default', async () => {
const otherResponse = 'other response'
fetch.once(otherResponse)
await expectMocked(defaultRequestUri, otherResponse)
await expectMocked()
})
it('dont mock once then mock twice', async () => {
const otherResponse = 'other response'
fetch
.dontMockOnce()
.once(otherResponse)
.once(otherResponse)

await expectUnmocked()
await expectMocked(defaultRequestUri, otherResponse)
await expectMocked()
})
})

describe('doMockIf', () => {
it("doesn't mock normally", async () => {
fetch.doMockIf('http://foo')
await expectUnmocked()
await expectUnmocked()
})
it('mocks when matches string', async () => {
fetch.doMockIf(testUrl)
await expectMocked()
await expectMocked()
})
it('mocks when matches regex', async () => {
fetch.doMockIf(new RegExp(testUrl))
await expectMocked()
await expectMocked()
})
it('mocks when matches predicate', async () => {
fetch.doMockIf(input => input.url === testUrl)
await expectMocked()
await expectMocked()
})
})

describe('dontMockIf', () => {
it('mocks normally', async () => {
fetch.dontMockIf('http://foo')
await expectMocked()
await expectMocked()
})
it('doesnt mock when matches string', async () => {
fetch.dontMockIf(testUrl)
await expectUnmocked()
await expectUnmocked()
})
it('doesnt mock when matches regex', async () => {
fetch.dontMockIf(new RegExp(testUrl))
await expectUnmocked()
await expectUnmocked()
})
it('doesnt mock when matches predicate', async () => {
fetch.dontMockIf(input => input.url === testUrl)
await expectUnmocked()
await expectUnmocked()
})
})

describe('doMockOnceIf (default mocked)', () => {
it("doesn't mock normally", async () => {
fetch.doMockOnceIf('http://foo')
await expectUnmocked()
await expectMocked()
})
it('mocks when matches string', async () => {
fetch.doMockOnceIf(testUrl)
await expectMocked()
await expectMocked()
})
it('mocks when matches regex', async () => {
fetch.doMockOnceIf(new RegExp(testUrl))
await expectMocked()
await expectMocked()
})
it('mocks when matches predicate', async () => {
fetch.doMockOnceIf(input => input.url === testUrl)
await expectMocked()
await expectMocked()
})
})

describe('dontMockOnceIf (default mocked)', () => {
it('mocks normally', async () => {
fetch.dontMockOnceIf('http://foo')
await expectMocked()
await expectMocked()
})
it('doesnt mock when matches string', async () => {
fetch.dontMockOnceIf(testUrl)
await expectUnmocked()
await expectMocked()
})
it('doesnt mock when matches regex', async () => {
fetch.dontMockOnceIf(new RegExp(testUrl))
await expectUnmocked()
await expectMocked()
})
it('doesnt mock when matches predicate', async () => {
fetch.dontMockOnceIf(input => input.url === testUrl)
await expectUnmocked()
await expectMocked()
})
})

describe('doMockOnceIf (default unmocked)', () => {
beforeEach(() => {
fetch.dontMock()
})
it("doesn't mock normally", async () => {
fetch.doMockOnceIf('http://foo')
await expectUnmocked()
await expectUnmocked()
})
it('mocks when matches string', async () => {
fetch.doMockOnceIf(testUrl)
await expectMocked()
await expectUnmocked()
})
it('mocks when matches regex', async () => {
fetch.doMockOnceIf(new RegExp(testUrl))
await expectMocked()
await expectUnmocked()
})
it('mocks when matches predicate', async () => {
fetch.doMockOnceIf(input => input.url === testUrl)
await expectMocked()
await expectUnmocked()
})
})

describe('dontMockOnceIf (default unmocked)', () => {
beforeEach(() => {
fetch.dontMock()
})
it('mocks normally', async () => {
fetch.dontMockOnceIf('http://foo')
await expectMocked()
await expectUnmocked()
})
it('doesnt mock when matches string', async () => {
fetch.dontMockOnceIf(testUrl)
await expectUnmocked()
await expectUnmocked()
})
it('doesnt mock when matches regex', async () => {
fetch.dontMockOnceIf(new RegExp(testUrl))
await expectUnmocked()
await expectUnmocked()
})
it('doesnt mock when matches predicate', async () => {
fetch.dontMockOnceIf(input => input.url === testUrl)
await expectUnmocked()
await expectUnmocked()
})
})

describe('dont/do mock', () => {
test('dontMock', async () => {
fetch.dontMock()
await expectUnmocked()
await expectUnmocked()
})
test('dontMockOnce', async () => {
fetch.dontMockOnce()
await expectUnmocked()
await expectMocked()
})
test('doMock', async () => {
fetch.dontMock()
fetch.doMock()
await expectMocked()
await expectMocked()
})
test('doMockOnce', async () => {
fetch.dontMock()
fetch.doMockOnce()
await expectMocked()
await expectUnmocked()
})
})

`

`js
vi.mock('fetch', async () => {
const fetchActual = globalThis.fetch;
const mocked = {};
for (const key of Object.keys(fetchActual)) {
if (typeof fetchActual[key] === 'function') {
mocked[key] = vi.fn(fetchActual[key]);
} else {
mocked[key] = fetchActual[key];
}
}
return mocked;
});

const expectMocked = async (uri, response = mockedDefaultResponse) => {
return expect(request(uri)).resolves.toEqual(response);
};
const expectUnmocked = async (uri) => {
return expect(request(uri)).resolves.toEqual(realResponse);
};

describe('conditional mocking complex', () => {
const realResponse = 'REAL FETCH RESPONSE';
const mockedDefaultResponse = 'MOCKED DEFAULT RESPONSE';
const testUrl = defaultRequestUri;
let fetchSpy;
beforeEach(() => {
fetch.resetMocks();
fetch.mockResponse(mockedDefaultResponse);
vi.mocked(fetch).mockImplementation(async () => Promise.resolve(new Response(realResponse)));
});

afterEach(() => {
vi.mocked(fetch).mockRestore();
});

describe('complex example', () => {
const alternativeUrl = 'http://bar';
const alternativeBody = 'ALTERNATIVE RESPONSE';
beforeEach(() => {
fetch
// .mockResponse(mockedDefaultResponse) // set above - here for clarity
.mockResponseOnce('1') // 1
.mockResponseOnce('2') // 2
.mockResponseOnce(async (uri) => (uri === alternativeUrl ? alternativeBody : '3')) // 3
.mockResponseOnce('4') // 4
.mockResponseOnce('5') // 5
.mockResponseOnce(async (uri) => (uri === alternativeUrl ? alternativeBody : mockedDefaultResponse)); // 6
});

describe('default (doMock)', () => {
beforeEach(() => {
fetch
// .doMock() // the default - here for clarify
.dontMockOnceIf(alternativeUrl)
.doMockOnceIf(alternativeUrl)
.doMockOnce()
.dontMockOnce();
});

test('defaultRequestUri', async () => {
await expectMocked(defaultRequestUri, '1'); // 1
await expectUnmocked(defaultRequestUri); // 2
await expectMocked(defaultRequestUri, '3'); // 3
await expectUnmocked(defaultRequestUri); // 4
// after .once('..')
await expectMocked(defaultRequestUri, '5'); // 5
await expectMocked(defaultRequestUri, mockedDefaultResponse); // 6
// default 'isMocked' (not 'Once')
await expectMocked(defaultRequestUri, mockedDefaultResponse); // 7
});

test('alternativeUrl', async () => {
await expectUnmocked(alternativeUrl); // 1
await expectMocked(alternativeUrl, '2'); // 2
await expectMocked(alternativeUrl, alternativeBody); // 3
await expectUnmocked(alternativeUrl); // 4
// after .once('..')
await expectMocked(alternativeUrl, '5'); // 5
await expectMocked(alternativeUrl, alternativeBody); // 6
// default 'isMocked' (not 'Once')
await expectMocked(alternativeUrl, mockedDefaultResponse); // 7
});
});

describe('dontMock', () => {
beforeEach(() => {
fetch.dontMock().dontMockOnceIf(alternativeUrl).doMockOnceIf(alternativeUrl).doMockOnce().dontMockOnce();
});

test('defaultRequestUri', async () => {
await expectMocked(defaultRequestUri, '1'); // 1
await expectUnmocked(defaultRequestUri); // 2
await expectMocked(defaultRequestUri, '3'); // 3
await expectUnmocked(defaultRequestUri); // 4
// after .once('..')
await expectUnmocked(defaultRequestUri); // 5
await expectUnmocked(defaultRequestUri); // 6
// default 'isMocked' (not 'Once')
await expectUnmocked(defaultRequestUri); // 7
});

test('alternativeUrl', async () => {
await expectUnmocked(alternativeUrl); // 1
await expectMocked(alternativeUrl, '2'); // 2
await expectMocked(alternativeUrl, alternativeBody); // 3
await expectUnmocked(alternativeUrl); // 4
// after .once('..')
await expectUnmocked(alternativeUrl); // 5
await expectUnmocked(alternativeUrl); // 6
// default 'isMocked' (not 'Once')
await expectUnmocked(alternativeUrl); // 7
});
});

describe('doMockIf(alternativeUrl)', () => {
beforeEach(() => {
fetch
.doMockIf(alternativeUrl)
.dontMockOnceIf(alternativeUrl)
.doMockOnceIf(alternativeUrl)
.doMockOnce()
.dontMockOnce();
});

test('defaultRequestUri', async () => {
await expectMocked(defaultRequestUri, '1'); // 1
await expectUnmocked(defaultRequestUri); // 2
await expectMocked(defaultRequestUri, '3'); // 3
await expectUnmocked(defaultRequestUri); // 4
// after .once('..')
await expectUnmocked(defaultRequestUri); // 5
await expectUnmocked(defaultRequestUri); // 6
// default 'isMocked' (not 'Once')
await expectUnmocked(defaultRequestUri); // 7
});

test('alternativeUrl', async () => {
await expectUnmocked(alternativeUrl); // 1
await expectMocked(alternativeUrl, '2'); // 2
await expectMocked(alternativeUrl, alternativeBody); // 3
await expectUnmocked(alternativeUrl); // 4
// after .once('..')
await expectMocked(alternativeUrl, '5'); // 5
await expectMocked(alternativeUrl, alternativeBody); // 6
// default 'isMocked' (not 'Once')
await expectMocked(alternativeUrl, mockedDefaultResponse); // 7
});
});

describe('dontMockIf(alternativeUrl)', () => {
beforeEach(() => {
fetch
.dontMockIf(alternativeUrl)
.dontMockOnceIf(alternativeUrl)
.doMockOnceIf(alternativeUrl)
.doMockOnce()
.dontMockOnce();
});

test('defaultRequestUri', async () => {
await expectMocked(defaultRequestUri, '1'); // 1
await expectUnmocked(defaultRequestUri); // 2
await expectMocked(defaultRequestUri, '3'); // 3
await expectUnmocked(defaultRequestUri); // 4
// after .once('..')
await expectMocked(defaultRequestUri, '5'); // 5
await expectMocked(defaultRequestUri, mockedDefaultResponse); // 6
// default 'isMocked' (not 'Once')
await expectMocked(defaultRequestUri, mockedDefaultResponse); // 7
});

test('alternativeUrl', async () => {
await expectUnmocked(alternativeUrl); // 1
await expectMocked(alternativeUrl, '2'); // 2
await expectMocked(alternativeUrl, alternativeBody); // 3
await expectUnmocked(alternativeUrl); // 4
// after .once('..')
await expectUnmocked(alternativeUrl); // 5
await expectUnmocked(alternativeUrl); // 6
// default 'isMocked' (not 'Once')
await expectUnmocked(alternativeUrl); // 7
});
});
});
});
``