Hello how could I test a function that receives a `Flow<T>` as a parameter and then inside has...

# coroutines

[Pablo]

Hello how could I test a function that receives a Flow<T> as a parameter and then inside has a collect { } ?

Example

fun doStuff(flow: Flow<String>) {
   scope.launch {
      flow.collect { 
        if(!it in myList) { 
           dataSource.add(it)
        }
      }
   }
}

How would I have this verify that dataSource.add(it) ? Considering this myList is something I can mock too

[Javier]

Checking data source before and after to see if it is adding what you expect

[Pablo]

Yes but how, I mean do I have to do something like :

runBlocking {
   myMethod.doStuff(flowOf("hello"))
}

[Pablo]

How would be the pseudo to test it?

[Javier]

You shouldn't need runBlocking, only the new runTest function. It allows advance the time too until the flow is completed

[Pablo]

but do I have to emit the value?

[Javier]

you mean the flowOf?

[Pablo]

yes

[Javier]

Probably you should test multiple scenarios

[Javier]

with empty list, with a unique list, another one to check if the if condition is working and so on