Unit test ClientProxy in Nestjs - unit-testing

Question

In Nestjs, I try to mock a ClientProxy but I receive a typing error telling me that I need to define all properties of ClientProxy class. Of course, I don't want to mock every property of this Class.
Any idea on how to solve this?
Here's a simplified piece of code:
service.ts
#Injectable()
export class SimulationsService {
constructor() {}
#Client({
transport: Transport.NATS,
options: {
url: env.nats,
user: env.usernats,
pass: env.passnats,
},
})
simulationClient: ClientProxy;
method1(){
this.simulationClient.send('simulatePattern', simulation)
.pipe(
map(sim=>{
//SOME CODE
return sim;
})
});
}
service.spec.ts
describe('method1', () => {
it('should return a processed Simulation', async () => {
jest.spyOn(
service,
'simulationClient',
'get',
).mockImplementation(()=>{
return {send() {
return of(simulationMock as Simulation);
}}
});
});
expect(await service.update('test', unfedSimulationMock)).toEqual(simulationMock);
});
});
Error output :
Type '{ send(): Observable; }' is missing the following properties from type 'ClientProxy': connect, close, routingMap, emit, and 7 more.

Answer 1

Here is a solution:
export interface ClientProxy {
send(pattern: string, simulation: any): any;
connect(): any;
close(): any;
routingMap(): any;
}
I simplify the code for service.ts:
// tslint:disable-next-line: interface-name
export interface ClientProxy {
send(pattern: string, simulation: any): any;
connect(): any;
close(): any;
routingMap(): any;
}
export class SimulationsService {
constructor(private simulationClient: ClientProxy) {}
public method1() {
const simulation = {};
this.simulationClient.send('simulatePattern', simulation);
}
}
Unit test, partial mock ClientProxy which means we can mock specific methods without the type error.
import { SimulationsService, ClientProxy } from './service';
import { mock } from '../../__utils';
const simulationClientMock = mock<ClientProxy>('send');
// Argument of type '{ send: Mock<any, any>; }' is not assignable to parameter of type 'ClientProxy'.
// Type '{ send: Mock<any, any>; }' is missing the following properties from type 'ClientProxy': connect, close, routingMap
// const simulationClientMock = {
// send: jest.fn()
// };
const service = new SimulationsService(simulationClientMock);
describe('SimulationsService', () => {
describe('#method1', () => {
it('t1', () => {
simulationClientMock.send.mockReturnValueOnce('mocked data');
service.method1();
expect(simulationClientMock.send).toBeCalledWith('simulatePattern', {});
});
});
});
__util.ts:
type GenericFunction = (...args: any[]) => any;
type PickByTypeKeyFilter<T, C> = {
[K in keyof T]: T[K] extends C ? K : never;
};
type KeysByType<T, C> = PickByTypeKeyFilter<T, C>[keyof T];
type ValuesByType<T, C> = {
[K in keyof T]: T[K] extends C ? T[K] : never;
};
type PickByType<T, C> = Pick<ValuesByType<T, C>, KeysByType<T, C>>;
type MethodsOf<T> = KeysByType<Required<T>, GenericFunction>;
type InterfaceOf<T> = PickByType<T, GenericFunction>;
type PartiallyMockedInterfaceOf<T> = {
[K in MethodsOf<T>]?: jest.Mock<InterfaceOf<T>[K]>;
};
export function mock<T>(...mockedMethods: Array<MethodsOf<T>>): jest.Mocked<T> {
const partiallyMocked: PartiallyMockedInterfaceOf<T> = {};
mockedMethods.forEach(mockedMethod => (partiallyMocked[mockedMethod] = jest.fn()));
return partiallyMocked as jest.Mocked<T>;
}
Unit test result with 100% coverage:
PASS src/stackoverflow/57960039/service.spec.ts
SimulationsService
#method1
✓ t1 (4ms)
----------------------------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
----------------------------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
src | 100 | 100 | 100 | 100 | |
__utils.ts | 100 | 100 | 100 | 100 | |
src/stackoverflow/57960039 | 100 | 100 | 100 | 100 | |
service.ts | 100 | 100 | 100 | 100 | |
----------------------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 3.234s, estimated 6s
Here is the completed demo: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/57960039