test: log uncaught exceptions in the demo smoke tests

AGENTS.md

@@ -76,6 +76,13 @@ and they are covered automatically. To run them with a device or emulator attach
 Add `-Pandroid.testInstrumentationRunnerArguments.requireMapLoaded=true` to also
 wait for map tiles to render, which needs a real key.
 
+On a physical device, keep the screen on for the whole run (for example
+`adb shell svc power stayon usb`, and `adb shell svc power stayon false`
+afterwards). If the screen times out in the middle, a demo can stop resuming and
+the run hangs with an ANR instead of failing (see #1070). The smoke tests also
+log any uncaught exception under the `DemoSmokeTest` tag, so check logcat if a
+run hangs.
+
 Running `maps-app` requires a Maps API key: put `MAPS_API_KEY=...` in
 `secrets.properties` at the repo root (see `local.defaults.properties` for the
 template). Never hardcode or commit API keys.

maps-app/src/androidTest/java/com/google/maps/android/compose/smoke/DemoAppSmokeTest.kt

@@ -17,6 +17,7 @@
 package com.google.maps.android.compose.smoke
 
 import android.graphics.Rect
+import android.util.Log
 import android.view.View
 import android.view.ViewGroup
 import androidx.activity.ComponentActivity
@@ -115,7 +116,10 @@ class DemoAppSmokeTest(private val demoName: String, private val demoActivity: C
         assumeTrue("Maps API key not specified", hasValidApiKey)
 
         defaultHandler = Thread.getDefaultUncaughtExceptionHandler()
-        Thread.setDefaultUncaughtExceptionHandler { _, throwable ->
+        Thread.setDefaultUncaughtExceptionHandler { thread, throwable ->
+            // Log it: if the main thread dies here the app hangs and the test may never reach
+            // assertNoUncaughtExceptions(), so logcat is the only place it would show up.
+            Log.e(TAG, "Uncaught exception on thread ${thread.name}", throwable)
             uncaughtExceptions.add(throwable)
         }
     }
@@ -270,3 +274,5 @@ class DemoAppSmokeTest(private val demoName: String, private val demoActivity: C
         walk(this@mapSurfaces)
     }
 }
+
+private const val TAG = "DemoSmokeTest"

maps-app/src/androidTest/java/com/google/maps/android/compose/smoke/DemoMenuNavigationTest.kt

@@ -18,6 +18,7 @@ package com.google.maps.android.compose.smoke
 
 import android.app.Activity
 import android.os.SystemClock
+import android.util.Log
 import android.view.View
 import android.view.ViewGroup
 import androidx.compose.ui.test.hasScrollToIndexAction
@@ -77,7 +78,10 @@ class DemoMenuNavigationTest(
     @Before
     fun setUp() {
         defaultHandler = Thread.getDefaultUncaughtExceptionHandler()
-        Thread.setDefaultUncaughtExceptionHandler { _, throwable ->
+        Thread.setDefaultUncaughtExceptionHandler { thread, throwable ->
+            // Log it: if the main thread dies here the app hangs and the test may never reach
+            // assertNoUncaughtExceptions(), so logcat is the only place it would show up.
+            Log.e(TAG, "Uncaught exception on thread ${thread.name}", throwable)
             uncaughtExceptions.add(throwable)
         }
     }
@@ -209,3 +213,5 @@ class DemoMenuNavigationTest(
         }
     }
 }
+
+private const val TAG = "DemoSmokeTest"