Suspending functions + unit tests An important pie...

# coroutines

[jmfayard]

Suspending functions + unit tests
An important piece of my code was buggy but covered by a correct test
... that was ignored because I mistakenly use a suspending function in a JUnit class
Gosh it would be so much better if suspending functions were supported directly in Junit instead of the runTest { ... } hack
The issue is there https://github.com/junit-team/junit5/issues/1914
but very little happened since 3 years

I created an issue, please star ⭐️ https://youtrack.jetbrains.com/issue/KT-52818/Provide-a-quick-fix-against-using-suspending-functions-in-Unit-Test

[stojan]

not sure if changing the test framework is an option for you, but #kotest supports suspend functions by default

[jmfayard]

I love kotest but here not really an option

[ephemient]

you can explore whether JUnit 5's extension system will allow you to handle suspend tests, but I suspect it's not possible

[jmfayard]

I guessed the issue above would be marked as fixed if that was possible 🙂

[ephemient]

so I played around with it a little
• the IDE already displays an error on @kotlinx.test.Test suspend fun
• a JUnit5 extension could wrap every test in runTest and inject scope/continuation parameters, but it can't change test discovery, which means no way around JUnit ignoring all suspend funs

[jmfayard]

Importing @Test from kotlin.test doesn't work,
it always import org.unit.jupiter.api.Test which doesn't give me the error,
unless I expeclitely type @kotlin.test.Test which is not very convenient....

[ephemient]

that error might be down to your IDE configuration; auto-complete allows both for me

[ephemient]

I did think of a way to get JUnit to run suspend tests, though. it involves a couple of nested extensions, and isn't able to fully participate in the JUnit test lifecycle, but it is possible to write the following test:

class ExampleTest : CoroutineTest {
    @Test
    suspend fun test() {
        println("OK")
    }
}

CoroutineTest_kt.kt

[jmfayard]

wow, thanks!