How do I mock redis when using supertest in Express? - express

Question

I am building a REST API in Express and I'm trying to mock Redis in my Jasmine unit tests (using redis-mock).
If supertest is making a request to the API, how do I tell my app to use the mock Redis instead of the actual redis? .I know I'll probably need to create separate modules for redis that I can swap out somehow, just not sure how to swap it out for a regular request vs a supertest request.
Unit test:
describe('Instance API v1', () => {
it('returns a list of instances', (done) => {
request(app.default)
.get('/v1/instance')
.set('Authorization', 'Bearer '+authToken)
.expect(200)
.expect('Content-Type', 'application/json; charset=utf-8')
.end((error) => (error) ? done.fail(error) : done());
});
});
Route handler:
getAll = (request: express.Request, response: express.Response) => {
let redis: RedisClient = request.app.locals.redisclient;
let keys:string[] = [];
let prefix = 'instance/*';
const scanner = new RedisScan(redis);
scanner.scan('instances/*', (err, matchingKeys) => {
if (err) throw(err);
// matchingKeys will be an array of strings if matches were found
// otherwise it will be an empty array.
console.log(matchingKeys);
response.json(matchingKeys);
});
};

Answer 1

in my previous experience, I didn't mock Redis in integration test so I can test the flow in full functionality.
If you want to mock the Redis, you must do it before you require and initiate your application in the test something like:
before(function() {
const matchingKeys = '1234';
sinon.stub(RedisScan.prototype, 'scan').yields(null, matchingKeys);
const app = require('./app');
return app.init(); // your init or whatever function to initiate your express app
});
Hope it helps