Mocking abstract methods

[themicp]

Hello everyone. Working with the examples on version 2.3.0, I have created the following test:

abstract class Foo {
  abstract getBar (num: number): string;
}

// Creating mock
let mockedFoo: Foo = mock(Foo)

// stub method before execution
when(mockedFoo.getBar(3)).thenReturn('three')

// Getting instance
let foo: Foo = instance(mockedFoo)

// prints three
console.log(foo.getBar(3))

// prints null, because "getBar(999)" was not stubbed
console.log(foo.getBar(999))

Expected output

three
null

Actual output

TypeError: mockedFoo.getBar is not a function

If I try to mock a concrete method on an abstract class however, the test works as expected.

[sbarlabanov]

Same problem for 2.3.1.

As a workaround one can create an abstract subclass with an empty implementation of the target method and use that subclass for mocking.

abstract class Foo {
  abstract getBar (num: number): string;
}

abstract class DummyFoo {
  getBar(num): any {};
}

// Creating mock
let mockedFoo: Foo = mock(DummyFoo)

[lordrip]

Another workaround could be mock the abstract class and use the method as a getter.

abstract class Foo {
  abstract getBar (num: number): string;
}

// Creating mock
let mockedFoo: Foo = mock(Foo)

// Using method as a get
when(mockedFoo.getBar)
  .thenReturn(() => undefined); // or your desired value

[mousedownmike]

Using the mock<Interface>() mechanism introduced in 2.4.0 for #117 , I no longer have this issue. I had previously been mocking a concrete implementation of my Abstract class but now I'm able to do something like:

export abstract class UserService {
  abstract registerUser(user: User): Promise<RegisterUserResult>;
}

const mockedUserService: UserService = mock<UserService>();

when(mockedUserService.registerUser(anything())).thenResolve({userId: '1234'});

I'm pretty new in the TS world so I could very well be missing something important.