pact-foundationJest-Pact
Jest Adaptor to help write Pact files with ease
Features
- [x] instantiates the PactOptions for you
- [x] Setups Pact mock service before and after hooks so you don’t have to
- [x] Set Jest timeout to 30 seconds preventing brittle tests in slow environments like Docker
- [x] Sensible defaults for the pact options that make sense with Jest
- [x] Supports both the main release of pact-js (9.x.x) and the beta 10.x.x for Pact spec V3
Jest-Pact Roadmap
- [ ] Ensure that jest-pact plays well with jest's default of watch-mode (This has been mothballed, please see this draft pr for details. Contributions welcome!
- [ ] Ensure that pact failures print nice diffs (at the moment you have to go digging in the log files)
- [ ] Add a setup hook for clearing out log and pact files
Adapter Installation
npm install --save-dev jest-pact
yarn add jest-pact --dev
If you have more than one file with pact tests for the same consumer/provider
pair, you will also need to add --runInBand to your jest or react-scripts test command in your package.json. This avoids race conditions with the mock
server writing to the pact file.
Usage - Pact-JS V2
Say that your API layer looks something like this:
import axios from 'axios';
const defaultBaseUrl = 'http://your-api.example.com';
export const api = (baseUrl = defaultBaseUrl) => ({
getHealth: () =>
axios.get(`${baseUrl}/health`).then((response) => response.data.status),
/* other endpoints here */
});
Then your test might look like:
import { pactWith } from 'jest-pact';
import { Matchers } from '@pact-foundation/pact';
import api from 'yourCode';
pactWith({ consumer: 'MyConsumer', provider: 'MyProvider' }, provider => {
let client;
beforeEach(() => {
client = api(provider.mockService.baseUrl)
});
describe('health endpoint', () => {
// Here we set up the interaction that the Pact
// mock provider will expect.
//
// jest-pact takes care of validating and tearing
// down the provider for you.
beforeEach(() => // note the implicit return.
// addInteraction returns a promise.
// If you don't want to implicitly return,
// you will need to `await` the result
provider.addInteraction({
state: "Server is healthy",
uponReceiving: 'A request for API health',
willRespondWith: {
status: 200,
body: {
status: Matchers.like('up'),
},
},
withRequest: {
method: 'GET',
path: '/health',
},
})
);
// You also test that the API returns the correct
// response to the data layer.
//
// Although Pact will ensure that the provider
// returned the expected object, you need to test that
// your code receives the right object.
//
// This is often the same as the object that was
// in the network response, but (as illustrated
// here) not always.
it('returns server health', () => // implicit return again
client.getHealth().then(health => {
expect(health).toEqual('up');
}));
});
});
Usage - Pact-JS V3
We also include a wrapper for Pact-JS V3.
Note: The API is NOT finalised. Feedback welcome
If you have thoughts or feedback about the DSL, please let us know via slack or open issue.
Currently, only a default for the pact directory is provided by the jest-pact wrapper jest-pact/dist/v3.
import { pactWith } from 'jest-pact/dist/v3';
import { MatchersV3 } from '@pact-foundation/pact';
import api from 'yourCode';
pactWith({ consumer: 'MyConsumer', provider: 'MyProvider' }, (interaction) => {
interaction('A request for API health', ({ provider, execute }) => {
beforeEach(() =>
provider
.given('Server is healthy')
.uponReceiving('A request for API health')
.withRequest({
method: 'GET',
path: '/health',
})
.willRespondWith({
status: 200,
body: {
status: MatchersV3.like('up'),
},
})
);
execute('some api call', (mockserver) =>
api(mockserver.url)
.health()
.then((health) => {
expect(health).toEqual('up');
})
);
});
});
Best practices
You can make your tests easier to read by extracting your request and responses:
/* pact.fixtures.js */
import { Matchers } from '@pact-foundation/pact';
export const healthRequest = {
uponReceiving: 'A request for API health',
withRequest: {
method: 'GET',
path: '/health',
},
};
export const healthyResponse = {
status: 200,
body: {
status: Matchers.like('up'),
},
};
import { pactWith } from 'jest-pact';
import { healthRequest, healthyResponse } from "./pact.fixtures";
import api from 'yourCode';
pactWith({ consumer: 'MyConsumer', provider: 'MyProvider' }, provider => {
let client;
beforeEach(() => {
client = api(provider.mockService.baseUrl)
});
describe('health endpoint', () => {
beforeEach(() =>
provider.addInteraction({
state: "Server is healthy",
...healthRequest,
willRespondWith: healthyResponse
})
);
it('returns server health', () =>
client.getHealth().then(health => {
expect(health).toEqual('up');
}));
});
Common gotchas
- Forgetting to wait for the promise from
addInteractioninbeforeEach. You can return the promise, or useasync/await. If you forget this, your interaction may not be set up before the test runs. - Forgetting to wait for the promise of your API call in
it. You can return the promise, or useasync/await. If you forget this, your test may pass before theexpectassertion runs, causing a potentially false success. - Not running jest with
--runInBand. If you have multiple test files that write to the same contract, you will need this to avoid intermittent failures when writing the contract file. - It's a good idea to specify a different log file for each invocation of
pactWith, otherwise the logs will get overwritten when other specs start. If you provide an explicit port, then the default mockserver log filename includes the port number.
API Documentation
Jest-Pact has two primary functions:
pactWith(JestPactOptions, (providerMock) => { /* tests go here */ }): a wrapper that sets up a pact mock provider, applies sensible default options, and applies the setup and verification hooks so you don't have tomessagePactWith(JestMessageConsumerOptions, (messagePact) => { /* tests go here */ }): a wrapper that sets up a message pact instance and applies sensible default options
Additionally, pactWith.only / fpactWith, pactWith.skip / xpactWith, messagePactWith.only / fmessagePactWith and messagePactWith.skip / xmessagePactWith behave as you would expect from Jest.
There are two types exported:
JestProvidedPactFn: This is the type of the second argument topactWith, ie:(provider: Pact) => voidJestPactOptions: An extended version ofPactOptionsthat has some additional convienience options (see below).
Configuration
You can use all the usual PactOptions from pact-js, plus a timeout for
telling jest to wait a bit longer for pact to start and run.
pactWith(JestPactOptions, (provider) => {
// regular http pact tests go here
});
messagePactWith(JestMessageConsumerOptions, (messagePact) => {
// regular message pact tests go here
});
interface ExtraOptions {
timeout?: number; // Timeout for pact service start/teardown, expressed in milliseconds
// Default is 30000 milliseconds (30 seconds).
logDir?: string; // path for the log file
logFileName?: string; // filename for the log file
}
type JestPactOptions = PactOptions & ExtraOptions;
type JestMessageConsumerOptions = MessageConsumerOptions & ExtraOptions;
Defaults
Jest-Pact sets some helpful default PactOptions for you. You can override any of these by explicitly setting corresponding option. Here are the defaults:
logis set so that log files are written to/pact/logs, and named<consumer>-<provider>-mockserver-interaction.log. If you provided an explicitport, then the log file name is<consumer>-<provider>-mockserver-interaction-port-<portNumber>.logdiris set so that pact files are written to/pact/pactslogLevelis set to warntimeoutis 30,000 milliseconds (30 seconds)pactfileWriteModeis set to "update"
Most of the time you won't need to change these.
A common use case for log is to change only the filename or the path for
logging. To help with this, Jest-Pact provides convenience options logDir
and logFileName. These allow you to set the path or the filename
independently. In case you're wondering, if you specify log, logDir and
logFileName, the convenience options are ignored and log takes
precedence.
Jest Watch Mode
By default Jest will watch all your files for changes, which means it will run in an infinite loop as your pact tests will generate json pact files and log files.
You can get around this by using the following watchPathIgnorePatterns: ["pact/logs/*","pact/pacts/*"] in your jest.config.js
Example
module.exports = {
testMatch: ['**/*.test.(ts|js)', '**/*.it.(ts|js)', '**/*.pacttest.(ts|js)'],
watchPathIgnorePatterns: ['pact/logs/*', 'pact/pacts/*'],
};
You can now run your tests with jest --watch and when you change a pact file, or your source code, your pact tests will run
Examples of usage of jest-pact
See Jest-Pact-Typescript which showcases a full consumer workflow written in Typescript with Jest, using this adaptor
- [x] Example pact tests
- [x] AWS v4 Signed API Gateway Provider
- [x] Soap API provider
- [x] File upload API provider
- [x] JSON API provider
Examples Installation
- clone repository
git@github.com:YOU54F/jest-pact-typescript.git - Run
yarn install - Run
yarn run pact-test
Generated pacts will be output in pact/pacts
Log files will be output in pact/logs