Add test for push distributor change.

libraries/pushproviders/test/src/main/kotlin/io/element/android/libraries/pushproviders/test/FakePushProvider.kt

@@ -25,7 +25,7 @@ class FakePushProvider(
     override val index: Int = 0,
     override val name: String = "aFakePushProvider",
     private val isAvailable: Boolean = true,
-    private val distributors: List<Distributor> = emptyList()
+    private val distributors: List<Distributor> = listOf(Distributor("aDistributorValue", "aDistributorName")),
 ) : PushProvider {
     override fun isAvailable(): Boolean = isAvailable
 
@@ -36,7 +36,7 @@ class FakePushProvider(
     }
 
     override suspend fun getCurrentDistributor(matrixClient: MatrixClient): Distributor? {
-        return null
+        return distributors.firstOrNull()
     }
 
     override suspend fun unregister(matrixClient: MatrixClient): Result<Unit> {