Improve coverage for `TimelinePresenter`

features/messages/src/test/kotlin/io/element/android/features/messages/timeline/TimelinePresenterTest.kt

@@ -22,6 +22,8 @@ import app.cash.molecule.RecompositionClock
 import app.cash.molecule.moleculeFlow
 import app.cash.turbine.test
 import com.google.common.truth.Truth.assertThat
+import io.element.android.features.messages.timeline.model.TimelineItem
+import io.element.android.libraries.matrix.timeline.MatrixTimelineItem
 import io.element.android.libraries.matrixtest.FakeMatrixClient
 import io.element.android.libraries.matrixtest.core.A_ROOM_ID
 import io.element.android.libraries.matrixtest.room.FakeMatrixRoom
@@ -43,7 +45,7 @@ class TimelinePresenterTest {
             presenter.present()
         }.test {
             val initialState = awaitItem()
-            assertThat(initialState.timelineItems.size).isEqualTo(0)
+            assertThat(initialState.timelineItems).isEmpty()
         }
     }
 
@@ -90,4 +92,26 @@ class TimelinePresenterTest {
             assertThat(withoutHighlightedState.highlightedEventId).isNull()
         }
     }
+
+    @Test
+    fun `present - test callback`() = runTest {
+        val matrixTimeline = FakeMatrixTimeline()
+        val matrixRoom = FakeMatrixRoom(A_ROOM_ID, matrixTimeline = matrixTimeline)
+        val presenter = TimelinePresenter(
+            testCoroutineDispatchers(),
+            FakeMatrixClient(),
+            matrixRoom
+        )
+        moleculeFlow(RecompositionClock.Immediate) {
+            presenter.present()
+        }.test {
+            val initialState = awaitItem()
+            assertThat(initialState.timelineItems).isEmpty()
+            // Simulate callback from the SDK
+            matrixTimeline.callback?.onPushedTimelineItem(MatrixTimelineItem.Virtual)
+            val nonEmptyState = awaitItem()
+            assertThat(nonEmptyState.timelineItems).isNotEmpty()
+            assertThat(nonEmptyState.timelineItems[0]).isEqualTo(TimelineItem.Virtual("virtual_item_0"))
+        }
+    }
 }

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

@@ -30,10 +30,7 @@ const val AN_EVENT_ID_VALUE = "!anEventId"
 val AN_EVENT_ID = EventId(AN_EVENT_ID_VALUE)
 
 class FakeMatrixTimeline : MatrixTimeline {
-
-    override var callback: MatrixTimeline.Callback?
-        get() = null
-        set(value) {}
+    override var callback: MatrixTimeline.Callback? = null
 
     private var hasMoreToLoadValue: Boolean = true