# Class: MockPool
Extends: `undici.Pool`
A mock Pool class that implements the Pool API and is used by MockAgent to intercept real requests and return mocked responses.
## `new MockPool(origin, [options])`
Arguments:
* **origin** `string` - It should only include the **protocol, hostname, and port**.
* **options** `MockPoolOptions` - It extends the `Pool` options.
Returns: `MockPool`
### Parameter: `MockPoolOptions`
Extends: `PoolOptions`
* **agent** `Agent` - the agent to associate this MockPool with.
### Example - Basic MockPool instantiation
We can use MockAgent to instantiate a MockPool ready to be used to intercept specified requests. It will not do anything until registered as the agent to use and any mock request are registered.
```js
import { MockAgent } from 'undici'
const mockAgent = new MockAgent()
const mockPool = mockAgent.get('http://localhost:3000')
```
## Instance Methods
### `MockPool.intercept(options)`
This method defines the interception rules for matching against requests for a MockPool or MockPool. We can intercept multiple times on a single instance, but each intercept is only used once. For example if you expect to make 2 requests inside a test, you need to call `intercept()` twice. Assuming you use `disableNetConnect()` you will get `MockNotMatchedError` on the second request when you only call `intercept()` once.
When defining interception rules, all the rules must pass for a request to be intercepted. If a request is not intercepted, a real request will be attempted.
| Matcher type | Condition to pass |
|:------------:| -------------------------- |
| `string` | Exact match against string |
| `RegExp` | Regex must pass |
| `Function` | Function must return true |
Arguments:
* **options** `MockPoolInterceptOptions` - Interception options.
Returns: `MockInterceptor` corresponding to the input options.
### Parameter: `MockPoolInterceptOptions`
* **path** `string | RegExp | (path: string) => boolean` - a matcher for the HTTP request path. When a `RegExp` or callback is used, it will match against the request path including all query parameters in alphabetical order. When a `string` is provided, the query parameters can be conveniently specified through the `MockPoolInterceptOptions.query` setting.
* **method** `string | RegExp | (method: string) => boolean` - (optional) - a matcher for the HTTP request method. Defaults to `GET`.
* **body** `string | RegExp | (body: string) => boolean` - (optional) - a matcher for the HTTP request body.
* **headers** `Record<string, string | RegExp | (body: string) => boolean`> - (optional) - a matcher for the HTTP request headers. To be intercepted, a request must match all defined headers. Extra headers not defined here may (or may not) be included in the request and do not affect the interception in any way.
* **query** `Record<string, any> | null` - (optional) - a matcher for the HTTP request query string params. Only applies when a `string` was provided for `MockPoolInterceptOptions.path`.
### Return: `MockInterceptor`
We can define the behaviour of an intercepted request with the following options.
* **reply** `(statusCode: number, replyData: string | Buffer | object | MockInterceptor.MockResponseDataHandler, responseOptions?: MockResponseOptions) => MockScope` - define a reply for a matching request. You can define the replyData as a callback to read incoming request data. Default for `responseOptions` is `{}`.
* **reply** `(callback: MockInterceptor.MockReplyOptionsCallback) => MockScope` - define a reply for a matching request, allowing dynamic mocking of all reply options rather than just the data.
* **replyWithError** `(error: Error) => MockScope` - define an error for a matching request to throw.
* **defaultReplyHeaders** `(headers: Record<string, string>) => MockInterceptor` - define default headers to be included in subsequent replies. These are in addition to headers on a specific reply.
* **defaultReplyTrailers** `(trailers: Record<string, string>) => MockInterceptor` - define default trailers to be included in subsequent replies. These are in addition to trailers on a specific reply.
* **replyContentLength** `() => MockInterceptor` - define automatically calculated `content-length` headers to be included in subsequent replies.
The reply data of an intercepted request may either be a string, buffer, or JavaScript object. Objects are converted to JSON while strings and buffers are sent as-is.
By default, `reply` and `replyWithError` define the behaviour for the first matching request only. Subsequent requests will not be affected (this can be changed using the returned `MockScope`).
### Parameter: `MockResponseOptions`
* **headers** `Record<string, string>` - headers to be included on the mocked reply.
* **trailers** `Record<string, string>` - trailers to be included on the mocked reply.
### Return: `MockScope`
A `MockScope` is associated with a single `MockInterceptor`. With this, we can configure the default behaviour of a intercepted reply.
* **delay** `(waitInMs: number) => MockScope` - delay the associated reply by a set amount in ms.
* **persist** `() => MockScope` - any matching request will always reply with the defined response indefinitely.
* **times** `(repeatTimes: number) => MockScope` - any matching request will reply with the defined response a fixed amount of times. This is overridden by **persist**.
#### Example - Basic Mocked Request
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
// MockPool
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({ path: '/foo' }).reply(200, 'foo')
const {
statusCode,
body
} = await request('http://localhost:3000/foo')
console.log('response received', statusCode) // response received 200
for await (const data of body) {
console.log('data', data.toString('utf8')) // data foo
}
```
#### Example - Mocked request using reply data callbacks
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/echo',
method: 'GET',
headers: {
'User-Agent': 'undici',
Host: 'example.com'
}
}).reply(200, ({ headers }) => ({ message: headers.get('message') }))
const { statusCode, body, headers } = await request('http://localhost:3000', {
headers: {
message: 'hello world!'
}
})
console.log('response received', statusCode) // response received 200
console.log('headers', headers) // { 'content-type': 'application/json' }
for await (const data of body) {
console.log('data', data.toString('utf8')) // { "message":"hello world!" }
}
```
#### Example - Mocked request using reply options callback
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/echo',
method: 'GET',
headers: {
'User-Agent': 'undici',
Host: 'example.com'
}
}).reply(({ headers }) => ({ statusCode: 200, data: { message: headers.get('message') }})))
const { statusCode, body, headers } = await request('http://localhost:3000', {
headers: {
message: 'hello world!'
}
})
console.log('response received', statusCode) // response received 200
console.log('headers', headers) // { 'content-type': 'application/json' }
for await (const data of body) {
console.log('data', data.toString('utf8')) // { "message":"hello world!" }
}
```
#### Example - Basic Mocked requests with multiple intercepts
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).reply(200, 'foo')
mockPool.intercept({
path: '/hello',
method: 'GET',
}).reply(200, 'hello')
const result1 = await request('http://localhost:3000/foo')
console.log('response received', result1.statusCode) // response received 200
for await (const data of result1.body) {
console.log('data', data.toString('utf8')) // data foo
}
const result2 = await request('http://localhost:3000/hello')
console.log('response received', result2.statusCode) // response received 200
for await (const data of result2.body) {
console.log('data', data.toString('utf8')) // data hello
}
```
#### Example - Mocked request with query body, request headers and response headers and trailers
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo?hello=there&see=ya',
method: 'POST',
body: 'form1=data1&form2=data2',
headers: {
'User-Agent': 'undici',
Host: 'example.com'
}
}).reply(200, { foo: 'bar' }, {
headers: { 'content-type': 'application/json' },
trailers: { 'Content-MD5': 'test' }
})
const {
statusCode,
headers,
trailers,
body
} = await request('http://localhost:3000/foo?hello=there&see=ya', {
method: 'POST',
body: 'form1=data1&form2=data2',
headers: {
foo: 'bar',
'User-Agent': 'undici',
Host: 'example.com'
}
})
console.log('response received', statusCode) // response received 200
console.log('headers', headers) // { 'content-type': 'application/json' }
for await (const data of body) {
console.log('data', data.toString('utf8')) // '{"foo":"bar"}'
}
console.log('trailers', trailers) // { 'content-md5': 'test' }
```
#### Example - Mocked request using different matchers
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: /^GET$/,
body: (value) => value === 'form=data',
headers: {
'User-Agent': 'undici',
Host: /^example.com$/
}
}).reply(200, 'foo')
const {
statusCode,
body
} = await request('http://localhost:3000/foo', {
method: 'GET',
body: 'form=data',
headers: {
foo: 'bar',
'User-Agent': 'undici',
Host: 'example.com'
}
})
console.log('response received', statusCode) // response received 200
for await (const data of body) {
console.log('data', data.toString('utf8')) // data foo
}
```
#### Example - Mocked request with reply with a defined error
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).replyWithError(new Error('kaboom'))
try {
await request('http://localhost:3000/foo', {
method: 'GET'
})
} catch (error) {
console.error(error) // Error: kaboom
}
```
#### Example - Mocked request with defaultReplyHeaders
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).defaultReplyHeaders({ foo: 'bar' })
.reply(200, 'foo')
const { headers } = await request('http://localhost:3000/foo')
console.log('headers', headers) // headers { foo: 'bar' }
```
#### Example - Mocked request with defaultReplyTrailers
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).defaultReplyTrailers({ foo: 'bar' })
.reply(200, 'foo')
const { trailers } = await request('http://localhost:3000/foo')
console.log('trailers', trailers) // trailers { foo: 'bar' }
```
#### Example - Mocked request with automatic content-length calculation
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).replyContentLength().reply(200, 'foo')
const { headers } = await request('http://localhost:3000/foo')
console.log('headers', headers) // headers { 'content-length': '3' }
```
#### Example - Mocked request with automatic content-length calculation on an object
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).replyContentLength().reply(200, { foo: 'bar' })
const { headers } = await request('http://localhost:3000/foo')
console.log('headers', headers) // headers { 'content-length': '13' }
```
#### Example - Mocked request with persist enabled
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).reply(200, 'foo').persist()
const result1 = await request('http://localhost:3000/foo')
// Will match and return mocked data
const result2 = await request('http://localhost:3000/foo')
// Will match and return mocked data
// Etc
```
#### Example - Mocked request with times enabled
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET'
}).reply(200, 'foo').times(2)
const result1 = await request('http://localhost:3000/foo')
// Will match and return mocked data
const result2 = await request('http://localhost:3000/foo')
// Will match and return mocked data
const result3 = await request('http://localhost:3000/foo')
// Will not match and make attempt a real request
```
#### Example - Mocked request with path callback
```js
import { MockAgent, setGlobalDispatcher, request } from 'undici'
import querystring from 'querystring'
const mockAgent = new MockAgent()
setGlobalDispatcher(mockAgent)
const mockPool = mockAgent.get('http://localhost:3000')
const matchPath = requestPath => {
const [pathname, search] = requestPath.split('?')
const requestQuery = querystring.parse(search)
if (!pathname.startsWith('/foo')) {
return false
}
if (!Object.keys(requestQuery).includes('foo') || requestQuery.foo !== 'bar') {
return false
}
return true
}
mockPool.intercept({
path: matchPath,
method: 'GET'
}).reply(200, 'foo')
const result = await request('http://localhost:3000/foo?foo=bar')
// Will match and return mocked data
```
### `MockPool.close()`
Closes the mock pool and de-registers from associated MockAgent.
Returns: `Promise<void>`
#### Example - clean up after tests are complete
```js
import { MockAgent } from 'undici'
const mockAgent = new MockAgent()
const mockPool = mockAgent.get('http://localhost:3000')
await mockPool.close()
```
### `MockPool.dispatch(options, handlers)`
Implements [`Dispatcher.dispatch(options, handlers)`](Dispatcher.md#dispatcherdispatchoptions-handler).
### `MockPool.request(options[, callback])`
See [`Dispatcher.request(options [, callback])`](Dispatcher.md#dispatcherrequestoptions-callback).
#### Example - MockPool request
```js
import { MockAgent } from 'undici'
const mockAgent = new MockAgent()
const mockPool = mockAgent.get('http://localhost:3000')
mockPool.intercept({
path: '/foo',
method: 'GET',
}).reply(200, 'foo')
const {
statusCode,
body
} = await mockPool.request({
origin: 'http://localhost:3000',
path: '/foo',
method: 'GET'
})
console.log('response received', statusCode) // response received 200
for await (const data of body) {
console.log('data', data.toString('utf8')) // data foo
}
```
