# Kotlin unit test failing when using generics and Mockito

**URL:** https://discuss.kotlinlang.org/t/kotlin-unit-test-failing-when-using-generics-and-mockito/1866
**Category:** Support
**Created:** [July 14, 2016, 8:46pm UTC](https://discuss.kotlinlang.org/t/kotlin-unit-test-failing-when-using-generics-and-mockito/1866 "2016-07-14T20:46:11Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![kotlinnewb](https://avatars.discourse-cdn.com/v4/letter/k/48db29/32.png) [@kotlinnewb](https://discuss.kotlinlang.org/u/kotlinnewb)
#### Post date: [July 14, 2016, 8:46pm UTC](https://discuss.kotlinlang.org/t/kotlin-unit-test-failing-when-using-generics-and-mockito/1866/1 "2016-07-14T20:46:11Z")

</div>

The test is using this interface:

```java
public interface View<T extends Model> {
  void onModelLoad(T model)
}

```

After using IntelliJ’s “Convert to Kotlin” action I have this:

```kotlin
// this has an error: only classes are allowed on the left hand side of a class literal
val view = mock<View<MyModel>>(View<MyModel>::class.java)
// testing the method on the interface with Mockito
verify(view, times(1)).onModelLoad(any(MyModel::class.java))

```

The original Java was:

```java
View view = mock(View.class);
// there is a warning on the line below about an unchecked cast, 
// but the code compiles and the test is successful:
verify(view, times(1)).onModelLoad(any(CkModel.class));

```

When I try to move the class to the left-hand side per the error message I get an inference error:

```kotlin
// the error here is: type inference failed, expected type mismatch: required View<MyModel>, found View<*>!
val view: View<MyModel> = mock(View::class.java)

```

Changing it to the following results in a different error:

```kotlin
val view = mock(View::class.java)
// out-projected type 'View<*>!' prohibits the use of 
// 'public abstract fun onModelLoad(T model):Unit defined in 'com...View'
verify(view, times(1)).onModelLoad(any(MyModel::class.java))

```

I managed to get the code below to work. But it is a bit much, and I have multiple tests where I would need to add these unchecked casts in a lot of places:

```kotlin
@Suppress("UNCHECKED_CAST")
val view: View<MyModel> = mock(View::class.java) as View<MyModel>
verify(view, times(1)).onModelLoad(any(MyModel::class.java))

```

The original code needs to be an interface w/ a generic, so I don’t see any reason to change it to accommodate the tests.

I’m at a loss as to how to do this cleanly. Being new to Kotlin I think I may be doing something wrong but am unsure and unable to find help online for this.

Thanks for any help.

---

<div class="post-metadata">

### Author: ![vbezhenar](https://avatars.discourse-cdn.com/v4/letter/v/35a633/32.png) [@vbezhenar](https://discuss.kotlinlang.org/u/vbezhenar)
#### Post date: [July 15, 2016, 3:00am UTC](https://discuss.kotlinlang.org/t/kotlin-unit-test-failing-when-using-generics-and-mockito/1866/2 "2016-07-15T03:00:12Z")

</div>

Add helper function somewhere in your test package:

```auto
inline fun <reified T: Any> mock() = Mockito.mock(T::class.java)

```

and use it instead of Mockito’s:

```auto
val view: View<MyModel> = mock()

```

You can also use the following library which adds this and few other functions to better suit Mockito for Kotlin: [GitHub - mockito/mockito-kotlin: Using Mockito with Kotlin](https://github.com/nhaarman/mockito-kotlin/)