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kotlinlang

How do I test the fails of a test that relies on a `suspend` funciton?

Let's consider this class

```
/**
 * Allows the login of a user based on his private key.
 */
class PerformLoginUseCase internal constructor(private val repository: AuthenticationRepository){

    /**
     * Logs the user into the system using the given [authKey].
     * @return the user data once the login has been successful.
     */
    suspend operator fun invoke(authKey: PrivateKey): UserData {
        return repository.login(authKey)
    }
}
```

I have the following test

```
@Test
fun useCaseThrowsExceptionWhenRepositoryDoes() {
    assertFailsWith(Throwable::class) {
        coEvery { repository.login(any()) } throws Throwable()
        GlobalScope.launch { performLogin(mockk()) }
    }
}
```

While this should work properly, it fails with an `assertionError`. I think the exception is not raised in time, so who should I do this?

Because you run background job that return immediately and there is no chance for  assertFailsWith catch it
It’s like this code, there is no way to catch exception in this case too
```assertFailsWith(Throwable::class) {
   thread { error("Some error") }
}```

use runBlocking instead of GlobalScope.launch

You shouldn’t use GlobalScope in tests (at least, I don’t see   good use cases for this)

and to test suspend functions just use runBlocking (suspend `@Test` functions are not supported yet, but will be soon)

It's a common test, and I can't use the `runBlocking` method inside. I don't know why, but wit hthe following dependencies, it is not included:

```
implementation deps.kotlin.stdlib.common
implementation deps.kotlinx.coroutines.common
implementation deps.kotlin.test.common
implementation deps.kotlin.test.annotations
implementation deps.kotlinx.coroutines.test
```

see this issue
<https://youtrack.jetbrains.com/issue/KT-22228>

also suspend test functions will be available in 1.3.30

Thank you very much. Any ETA on Kotlin 1.3.30?

as usual, will be available when will be ready %)

but first EAP already available (not sure tho that KT-22228 is available there)

but anyway, you can workaround it with expect/actual + dynamic type for JS