Hi i need to unit test some code that employs `GlobalScope` is there a Best Practice approach?

# coroutines

[Tower Guidev2]

Hi
i need to unit test some code that employs GlobalScope
is there a Best Practice approach?

[stojan]

inject the scope

OR

extract the logic into suspend fun , test that... then the only remaining untested part becomes GlobalScope.launch { myFun() } which is trivial

[ursus]

inject the dispatcher that drives your scope and make it synchrouns with Unconfined

Or depends what myfun is doing, if it emits stuff to a Flow then you can test it via turbine library and you can even keep the global scope

[Tower Guidev2]

i used GlobalScope.launch {} so that I could place disk reads/writes (AndroidKeyStore calls) off the main thread and also so they did not impact app start up time
im employing the google tink library (com.google.crypto.tink) for my in app encryption

[ursus]

fair enough

[ursus]

class Whatever(dispatcher) {
    private val scope = CoroutineScope(SupervisorJob() + dispatcher)

    fun foo() {
       scope.launch { ... }
    }
}

[ursus]

in real code pass in the Dispatchers.Io
in test code pass in Dispatchers.Unconfined

[Tower Guidev2]

i originally had an init{} method in my Application class however that seems to cause a Race Condition
as tink sometimes failes with a null pointer as shown by this stacktrace

java.lang.NullPointerException: 
  at com.google.crypto.tink.integration.android.SharedPrefKeysetReader.<init> (SharedPrefKeysetReader.java:60)
  at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.withSharedPref (AndroidKeysetManager.kt:162)

[Tower Guidev2]

in real code pass in the Dispatchers.Io

in test code pass in Dispatchers.Unconfined

this is not possible as the code is in my onCreate() function within my Application class

[ursus]

show me your code

[Tower Guidev2]

override fun onCreate() {
    super.onCreate()

    GlobalScope.launch(<http://Dispatchers.IO|Dispatchers.IO>) {
        manageTink()
    }

    if (BuildConfig.DEBUG) manageStrictMode()

    DynamicColors.applyToActivitiesIfAvailable(this@MyApplication)

    upgradeSecurityProvider()
    registerActivityLifecycleCallbacks(this@MyApplication)
}

[Tower Guidev2]

private fun manageTink() {
    try {
        AeadConfig.register()
        authenticatedEncryption = generateNewKeysetHandle().getPrimitive(Aead::class.java)
    } catch (e: GeneralSecurityException) {
        throw RuntimeException(e)
    } catch (e: IOException) {
        throw RuntimeException(e)
    }
}

[ursus]

okay and whats the issue? Id just wrap the thing as I shown in the snippet to make it testable

[ursus]

App.onCreate() {
    TinkInitializer(this, <http://Dispatcher.Io|Dispatcher.Io>)
}

``````

[ursus]

or have a explicit init function and dont do it in the ctor but it doesnt matter in your case, youre not doing anything there

[Tower Guidev2]

the issue was that my code looked like this before i refactored it....

e.g. i called manageTink() from an init block in my Application class

init {
        GlobalScope.launch(<http://Dispatchers.IO|Dispatchers.IO>) {
            manageTink()
        }
    }

and as i pass this@MyApplication within the manageTink() function "sometimes" the appContext was found to be null

[ursus]

yea dont do that, run everything in App.onCreate, there context will be 100% available