Currently, I am attempting to replicate a well-known process in Java development using TypeScript and JEST for practice. In this scenario, there is a Controller class that relies on a Service class. The connection between the two is established through the constructor of the Controller, making the presence of the Service mandatory.
To manage dependencies at runtime, I utilize a Dependency Injection (DI) library called tsyringe. This ensures that the DI container handles the instantiation of the Service and its injection into the Controller when required.
Here is the source code for the Controller:
import { scoped, Lifecycle } from "tsyringe";
import { RouteService } from "./RouteService";
import { RouteDTO } from "./view/RouteDTO";
@scoped(Lifecycle.ContainerScoped)
export class RouteController {
constructor(private routeService: RouteService) {}
public createRoute(route: RouteDTO): RouteDTO {
// business logic - meant for testing
if (isBusinessLogicValid) {
return this.routeService.saveRoute(route);
} else {
throw Error("Invalid business logic");
}
}
}
And here is the source code for the Service:
import { scoped, Lifecycle } from "tsyringe";
import { UserSession } from "../user/UserSession";
import { RouteDTO } from "./view/RouteDTO";
@scoped(Lifecycle.ContainerScoped)
export class RouteService {
constructor(
private userSession: UserSession
) {}
public saveRoute(route: RouteDTO): RouteDTO {
// contains business logic and handling persistence
return route;
}
}
I am striving to mock the RouteService class in a manner that eliminates the need for manual creation of an instance for unit testing purposes with the RouteController. If done manually, it would involve resolving all underlying dependencies (i.e., RouteController depends on RouteService, RouteService depends on UserSession, and so forth).
In Java, utilizing Mockito allows me to achieve something similar as shown below:
RouteService routeServiceMock = mock(RouteService.class);
// defining mock behavior on routeServiceMock
RouteController controller = new RouteController(routeServiceMock);
RouteDTO newDTO = createRouteDTO();
RouteDTO savedDTO = controller.save(newDTO);
assertThat(savedDTO).isEqualTo(newDTO);
//... other assertions
Upon reviewing Jest documentation, I have not found an equivalent approach. Is there a way to accomplish this? If yes, could someone provide guidance on how to proceed?