Use Espresso to wait for idle UI

PagingSample/app/build.gradle

@@ -75,4 +75,5 @@ dependencies {
     androidTestImplementation deps.atsl.runner
     androidTestImplementation deps.coroutines.test
     androidTestImplementation deps.truth
+    androidTestImplementation deps.espresso.contrib
 }

PagingSample/app/src/androidTest/java/paging/android/example/com/pagingsample/MainActivityTest.kt

@@ -20,6 +20,8 @@ import androidx.annotation.UiThread
 import androidx.recyclerview.widget.RecyclerView
 import androidx.test.core.app.ActivityScenario
 import androidx.test.core.app.ApplicationProvider
+import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.google.common.truth.Truth.assertThat
 import org.junit.Test
@@ -36,11 +38,15 @@ class MainActivityTest {
     fun showSomeResults() {
         val intent = Intent(ApplicationProvider.getApplicationContext(), MainActivity::class.java)
         intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
-        val scenario = ActivityScenario.launch<MainActivity>(intent)
-        scenario.onActivity { activity ->
-            val recyclerView: RecyclerView = activity.binding.cheeseList
+        ActivityScenario.launch<MainActivity>(intent)
+        onView(withId(R.id.cheeseList)).check { view, noViewFoundException ->
+            if (noViewFoundException != null) {
+                throw noViewFoundException
+            }
+
+            val recyclerView = view as RecyclerView
             assertThat(recyclerView.adapter).isNotNull()
             assertThat(recyclerView.adapter!!.itemCount).isGreaterThan(0)
         }
     }
-}
\ No newline at end of file
+}

PagingWithNetworkSample/app/build.gradle

@@ -87,6 +87,7 @@ dependencies {
     androidTestImplementation deps.atsl.runner
     androidTestImplementation deps.atsl.rules
     androidTestImplementation deps.arch_core.testing
+    androidTestImplementation deps.espresso.contrib
 
     testImplementation deps.junit
     testImplementation deps.coroutines.test

PagingWithNetworkSample/app/src/androidTest/java/com/android/example/paging/pagingwithnetwork/reddit/ui/RedditActivityTest.kt

@@ -18,9 +18,12 @@ package com.android.example.paging.pagingwithnetwork.reddit.ui
 
 import android.app.Application
 import android.content.Intent
-import androidx.test.annotation.UiThreadTest
+import androidx.recyclerview.widget.RecyclerView
 import androidx.test.core.app.ActivityScenario
 import androidx.test.core.app.ApplicationProvider
+import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.matcher.ViewMatchers.withId
+import com.android.example.paging.pagingwithnetwork.R
 import com.android.example.paging.pagingwithnetwork.reddit.DefaultServiceLocator
 import com.android.example.paging.pagingwithnetwork.reddit.ServiceLocator
 import com.android.example.paging.pagingwithnetwork.reddit.api.RedditApi
@@ -65,9 +68,8 @@ class RedditActivityTest(private val type: RedditPostRepository.Type) {
     }
 
     @Test
-    @UiThreadTest
     fun showSomeResults() {
-        val scenario = ActivityScenario.launch<RedditActivity>(
+        ActivityScenario.launch<RedditActivity>(
             RedditActivity.intentFor(
                 context = ApplicationProvider.getApplicationContext(),
                 type = type
@@ -76,8 +78,12 @@ class RedditActivityTest(private val type: RedditPostRepository.Type) {
             }
         )
 
-        scenario.onActivity { activity ->
-            val recyclerView = activity.binding.list
+        onView(withId(R.id.list)).check { view, noViewFoundException ->
+            if (noViewFoundException != null) {
+                throw noViewFoundException
+            }
+
+            val recyclerView = view as RecyclerView
             assertEquals(3, recyclerView.adapter?.itemCount)
         }
     }