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How can we mock `FirebaseAuth.getInstance().signInWithCustomToken(token).addOnCompleteListener{}`  and other Task like `addOnSuccessListener` and `addOnFailureListener`
using *MockK ?*

I used to do a similar thing like this:
```@MockK(relaxed = true)
private lateinit var mockTask: Task&lt;List&lt;FirebaseVisionBarcode&gt;&gt;```
```every { mockTask.addOnFailureListener(any()) } answers {
   firstArg&lt;OnFailureListener&gt;().onFailure(mockk())
   mockTask
}```
To mock invoke a failure

return real tasks, for example `Tasks.forException(...)`

for `FirebaseAuth.getInstance().signInWithCustomToken(token).addOnCompleteListener`
 i have created

```lateinit var mockAuthTask: Task&lt;AuthResult&gt;
...
beforeEachTest{
.....
every { mockAuthTask.addOnSuccessListener(any()) } answers { firstArg&lt;OnCompleteListener&lt;AuthResult&gt;&gt;().onComplete(mockk()) }
}```

but its not working how can i do it <@UUKM5CY3X>

<@UJBC14H8A> can you please give me more info

instead of whole mock stuff, just create dummy AuthResult and create real task:

```val result = AuthResult(...)
val authTask = Tasks.forResult(result)```

<@UJBC14H8A> but AuthResult is interface i don't know how to implement that class as Concrete

for this do i also have to update real code(UseCases,Repositories) or just tests? <@UJBC14H8A>, because i'm not in situation to update real UseCases or repositories i am just fixing mocking issues

actually i have tried as <@UUKM5CY3X> suggested, but i'm getting this `Failure(e=io.mockk.MockKException: no answer found for: Task(#17).getException())` i think i'm getting this because we are sending `AuthResult` as mockobject but now i don't know how to solve it :disappointed:

you can use `mockk()` instead of implementing AuthResult I guess

or you can create your own `FakeAuthResult` class that implements the interface

<@UJBC14H8A> actually `mock(relaxed=true)` worked

but this is mocked, but as you said don't mock tasks and return real, what is Tasks.forExceptions() and how can i return real tasks, is it going to connect to connect Firebase server and return real tasks ? <@UJBC14H8A>

Task is just a wraper that can return either result or exception

`Tasks.forResult(mockk())` is a good compromise

you don't mock the task, but you mock real value

but it would be even better if you don't mock anything and just return concrete AuthResult

Thanks <@UJBC14H8A> &amp; <@UUKM5CY3X>, both of yours solutions really helped me.

after working everything currently i'm getting
``` no answer found for: SomeClass(#3).setSomeVariable(dummy)```

how can i add `every` for setters of fields ?

Try here: <https://mockk.io/#property-backing-fields>