Timeline test: check timeline is initialized and disposed

libraries/matrixtest/src/main/kotlin/io/element/android/libraries/matrixtest/timeline/FakeMatrixTimeline.kt

@@ -31,6 +31,7 @@ class FakeMatrixTimeline(
 
     private val paginationState: MutableStateFlow<MatrixTimeline.PaginationState> = MutableStateFlow(initialPaginationState)
     private val timelineItems: MutableStateFlow<List<MatrixTimelineItem>> = MutableStateFlow(initialTimelineItems)
+    var isInitialized = false
 
     fun updatePaginationState(update: (MatrixTimeline.PaginationState.() -> MatrixTimeline.PaginationState)) {
         paginationState.value = update(paginationState.value)
@@ -62,9 +63,13 @@ class FakeMatrixTimeline(
         return Result.success(Unit)
     }
 
-    override fun initialize() = Unit
+    override fun initialize() {
+        isInitialized = true
+    }
 
-    override fun dispose() = Unit
+    override fun dispose() {
+        isInitialized = false
+    }
 
     override suspend fun sendMessage(message: String): Result<Unit> {
         return Result.success(Unit)