Utilities to easily stub Koa context and cookies. The utilities are designed to help you write unit tests for your Koa middleware without needing to set up any kind of actual server in your test environment. When test writing is easy and fun you'll want to write more tests. ✨😎
yarn add @shopify/jest-koa-mocks
The module has two named exports, createMockContext
and createMockCookies
.
You should usually be able to get away with most unit tests just using createMockContext
.
import {createMockContext, createMockCookies} from '@shopify/jest-koa-mocks';
This function allows you to create fully stubbable koa contexts for your tests.
export interface Options<
CustomProperties extends Object,
RequestBody = undefined
> {
url?: string;
method?: RequestMethod;
statusCode?: number;
session?: Dictionary<any>;
headers?: Dictionary<string>;
cookies?: Dictionary<string>;
state?: Dictionary<any>;
encrypted?: boolean;
host?: string;
requestBody?: RequestBody;
throw?: Function;
redirect?: Function;
customProperties?: CustomProperties;
}
createContext(options: Options)
In the simplest case you call createMockContext
, run your middleware passing the result in, and then assert against the context objects fields
import SillyViewCounterMiddleware from '../silly-view-counter';
import {createMockContext} from '@shopify/jest-koa-mocks';
describe('silly-view-counter', () => {
it('iterates and displays new ctx.state.views', async () => {
const ctx = createMockContext({state: {views: 31}});
await SillyViewCounterMiddleware(ctx);
expect(ctx.state.views).toBe(32);
expect(ctx.status).toBe(200);
expect(ctx.body).toBe({view: 32});
});
});
ctx.throw
and ctx.redirect
are defaulted to jest.fn()
s, allowing you to easily test that a request has redirected or thrown in your middleware.
import passwordValidator from '../password-validator';
import {createMockContext} from '@shopify/jest-koa-mocks';
describe('password-validator', () => {
it('throws if no password query parameter is present', async () => {
const ctx = createMockContext({url: '/validate'});
await passwordValidator(ctx);
expect(ctx.throw).toBeCalledWith(400);
});
it('redirects to /user if the password is correct', async () => {
const ctx = createMockContext({url: '/validate?password=correct'});
await passwordValidator(ctx);
expect(ctx.redirect).toBeCalledWith('/user');
});
});
ctx.cookies
is created using createMockCookies
.
import oAuthStart from '../';
import {createMockContext} from '@shopify/jest-koa-mocks';
describe('oauthStart', () => {
it('sets nonce cookie', () => {
const oAuthStart = createOAuthStart(baseConfig);
const ctx = createMockContext({
url: `https://myCoolApp.com/auth`,
});
oAuthStart(ctx);
expect(ctx.cookies.set).toBeCalledWith('shopifyNonce', fakeNonce);
});
});
createMockContext
allows you to pass a requestBody
and session
key by default, so you should be able to test applications using the common body parsing or session libraries simply and quickly.
import login from '../login';
import {createMockContext} from '@shopify/jest-koa-mocks';
describe('password-validator', () => {
it('sets session.user if body contains a valid password and username', async () => {
const ctx = createMockContext({
url: '/login',
requestBody: {
username: 'valid',
password: 'valid',
},
session: {},
});
await login(ctx);
expect(ctx.session.user).toMatchObject({
username: 'valid',
accessToken: 'dummy-access-token',
});
});
});
Creates a mock cookies instance.
const cookies = createMockCookies({
sessionID: 'something something',
store: 'shop1',
referrer: 'somewhere.io',
});
The returned object will have the signature
interface MockCookies {
set(key: string, value: string): void;
get(key: string): string;
responseStore: Map<string, string>;
requestStore: Map<string, string>;
}
The set
and get
functions are designed to mimic how actual koa cookie instances work. This means set
will set a value to the responseStore
, while get
will retrieve values from the requestStore
.
// will set to the response store
cookies.set('key', 'value');
// will get from the request store
cookies.get('key') !== 'value';
// => true
When testing against a mock cookies instance you can either assert against the set
/get
functions, or you can check if the appropriate value is in the expected store.
cookies.set('foo', 'bar');
expect(cookies.set).toBeCalledWith('foo', 'bar');
cookies.set('foo', 'bar');
expect(cookies.responseStore.get('foo')).toBe('bar');