Mock Classes without Decorators (e.g. @Controller() or @Injectable())

[schaeferto]

Hey guys,

I have one question and hope you could help me out here. Or at least push me into the right direction.
So, I would like to simply create a mock like you do in your example code:

class SomeClassToMock {
  constructor(private someService: SomeService) {
    this.someService.callMe();
  }
}

const compiledMock = await TestBed.solitary(SomeClassToMock)
  .mock(SomeService)
  .final({
    callMe: jest.fn().mockReturnValue('You called the mock!')
  }).compile();

But unlike in your example, I do not want to annotate the class SomeClassToMock with the DI annotations of nestjs, because I want to express, that the devs have to initialise this class with 'new' and not using DI.
If I would add the Injectable() annotation it starts working as expected.

Am I doing weird stuff here?
Could you please point out, why this is only working with the decorator on that class?

How would you create a mock of such a 'normal' - 'un-decorated' class? I thought about using suites for this because I like getting the type-hints inside the .final() and the auto-mocking of the dependencies from the constructor of the mocked class.

Thank you for any hints or comments!

[omermorad]

Hi @schaeferto,

Suites relies on metadata reflection, which means a class must be decorated with something like @Injectable() for it to work with the TestBed and its automatic mocking capabilities. If you want to mock a class manually without using TestBed, you can use the mock function from your doubles installed package (e.g. import { mock } from '@suites/doubles.<lib>). This approach enables you to create stubs, but you'll lose access to the full Suites API and its features, such as automatic dependency management and type hints.

I'm curious about what you're trying to achieve with this setup. There might be a more elegant solution that fits your needs better. Could you provide more details on your use case? This way, I can help you find the best approach.

[schaeferto]

Hey @omermorad,
sorry for the delay. I am using now a custom function which creates a simple Proxy object to create, what I need.
I did not found a suitable function in jest or @automock (@suites), for that.

export const createMock = <T>(methods: Partial<Record<keyof T, jest.Mock>> = {}): jest.Mocked<T> => {
  const mock: any = {};
  const handler = {
    get: (target: any, prop: string) => {
      if (!(prop in target)) {
        target[prop] = jest.fn();
      }
      return target[prop];
    },
  };
  const proxy = new Proxy(mock, handler);
  for (const method in methods) {
    proxy[method] = methods[method];
  }
  return proxy as jest.Mocked<T>;
};

This way I can create my dependencies like this:

  const dependency1: jest.Mocked<DependencyType1> = createMock();
  const dependency2: jest.Mocked<DependencyType2> = createMock();

  const testObject = new TestObject(dependency1, dependency2);

I can also pass an Object to createMock({}) with type hints etc. which is, what I needed. TestObject is a simple Class, no @Injectable().