Hi i need to unit test some code that employs `GlobalScope`

Question

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

stojan · Answer

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 · Answer

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 · Answer

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 · Answer

fair enough

ursus · Answer

```class Whatever dispatcher private val scope = CoroutineScope SupervisorJob + dispatcher fun foo scope launch ```

ursus · Answer

in real code pass in the <http Dispatchers Io|Dispatchers Io> in test code pass in Dispatchers Unconfined

Tower Guidev2 · Answer

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 lt init gt SharedPrefKeysetReader java 60 at com google crypto tink integration android AndroidKeysetManager$Builder withSharedPref AndroidKeysetManager kt 162 ```

Tower Guidev2 · Answer

gt in real code pass in the <http Dispatchers Io|Dispatchers Io> gt in test code pass in Dispatchers Unconfined this is not possible as the code is in my `onCreate ` function within my Application class

ursus · Answer

show me your code

Tower Guidev2 · Answer

``` 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 · Answer

```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 · Answer

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

ursus · Answer

```App onCreate TinkInitializer this <http Dispatcher Io|Dispatcher Io> ``` ``````

ursus · Answer

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 · Answer

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 · Answer

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