Mock middleware calls in Typescript testing - node.js

Question

I am trying to write tests for my Typescript Node.js application. I am using Mocha framework and Chai assertion library. Everything was working fine until custom middlewares(like authentication checking) were added. I tried using Sinon.JS to mock calls to this middleware, but I am having troubles to get it working. Any help would be appreciated.
My app.ts file looks as following:
class App {
public express: express.Application;
constructor() {
this.express = express();
this.routeConfig();
}
private routeConfig(): void {
CustomRouteConfig.init(this.express);
}
}
CustomRouteConfig file:
export default class CustomRouteConfig {
static init(app: express.Application) {
app.use('/:something', SomethingMiddleware);
app.use('/:something', SomeAuthenticationMiddleware);
app.use('/:something/route1/endpointOne', ControllerToTest);
app.use(NotFoundHandler);
app.use(ErrorHandler);
}
}
My ControllerToTest.ts file looks as following:
export class ControllerToTest {
router : Router;
constructor() {
this.router = Router();
this.registerRoutes();
}
public getData(req: Request, res: Response, next: NextFunction) {
//some logic to call Restful API and return data
}
private registerRoutes() {
this.router.get('/', this.getData.bind(this));
}
}
export default new ControllerToTest().router;
My SomethingMiddleware looks as following:
export class SomethingMiddleware {
something = (req: Request, res: Response, next: NextFunction) => {
//some logic to check if request is valid, and call next function for either valid or error situation
}
}
export default new SomethingMiddleware().something;
My test file for this scenario looks as following:
describe('baseRoute', () => {
it('should be json', () => {
return chai.request(app).get('/something/route1/endPointOne')
.then(res => {
expect(res.type).to.eql('application/json');
});
});
});
What is the best way to use Sinon.JS mocks or stubs in this situation? Also, if you think there is a better approach to write tests for this scenario, that would be appreciated as well.

Answer 1

I ended up using sinon stubs. I combined these with Mocha's before and after functions to control what happens when during testing some of the external libraries are called. Also, I have used this on database calls and middleware checks, as these are not of interest to my unit testing. Below is an example of how I did it.
describe("ControllerToTest", () => {
// Sinon stubs for mocking API calls
before(function () {
let databaseCallStub= sinon.stub(DatabaseClass, "methodOfInterest", () => {
return "some dummy content for db call";
});
let customMiddlewareStub= sinon.stub(MyCustomMiddleware, "customMiddlewareCheckMethod", () => {
return true;
});
let someExternalLibraryCall= sinon.stub(ExternalLibrary, "methodInExternalLibrary", () => {
return "some dummy data"
});
});
after(function () {
sinon.restore(DatabaseClass.methodOfInterest);
sinon.restore(MyCustomMiddleware.customMiddlewareCheckMethod);
sinon.restore(ExternalLibrary.methodInExternalLibrary);
});
it("should return data", () => {
return chai.request(app).get('/something/route1/endPointOne')
.then(res => {
expect(res.type).to.eql('application/json');
});
});