update

Author: VinayGuthal

firebase-messaging/src/main/java/com/google/firebase/messaging/SharedPreferencesQueue.java

@@ -21,6 +21,7 @@
 import androidx.annotation.GuardedBy;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
 import androidx.annotation.WorkerThread;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
@@ -35,7 +36,8 @@ final class SharedPreferencesQueue {
   private final String itemSeparator;
 
   @GuardedBy("internalQueue")
-  private final ArrayDeque<String> internalQueue = new ArrayDeque<>();
+  @VisibleForTesting
+  final ArrayDeque<String> internalQueue = new ArrayDeque<>();
 
   private final Executor syncExecutor;
 
@@ -176,13 +178,34 @@ public void beginTransaction() {
     bulkOperation = true;
   }
 
+  @VisibleForTesting
+  void beginTransactionSync() {
+    synchronized (internalQueue) {
+      beginTransaction();
+    }
+  }
+
   /** Commits bulk operation transactions. See {@link SharedPreferencesQueue#beginTransaction()}. */
   @GuardedBy("internalQueue")
   public void commitTransaction() {
     bulkOperation = false;
     syncStateAsync();
   }
 
+  @VisibleForTesting
+  void commitTransactionSync() {
+    synchronized (internalQueue) {
+      commitTransaction();
+    }
+  }
+
+  @VisibleForTesting
+  public String serializeSync() {
+    synchronized (internalQueue) {
+      return serialize();
+    }
+  }
+
   public boolean remove(@Nullable Object o) {
     synchronized (internalQueue) {
       return checkAndSyncState(internalQueue.remove(o));

firebase-messaging/src/test/java/com/google/firebase/messaging/SharedPreferencesQueueRoboTest.java

@@ -17,8 +17,6 @@
 import static java.util.concurrent.TimeUnit.SECONDS;
 
 import android.content.Context;
-
-import androidx.annotation.GuardedBy;
 import androidx.test.core.app.ApplicationProvider;
 import com.google.firebase.messaging.testing.FakeScheduledExecutorService;
 import org.junit.Before;
@@ -32,7 +30,6 @@ public class SharedPreferencesQueueRoboTest {
   private static final String TEST_TOPIC = "Test_Topic";
   private final FakeScheduledExecutorService executor = new FakeScheduledExecutorService();
 
-  @GuardedBy("this")
   private SharedPreferencesQueue queue;
 
   @Before
@@ -122,7 +119,7 @@ public void testSerialize() {
     queue.add(TEST_TOPIC + "1");
     queue.add(TEST_TOPIC + "3");
     queue.add(TEST_TOPIC + "2");
-    assertThat(queue.serialize())
+    assertThat(queue.serializeSync())
         .isEqualTo(
             TEST_TOPIC
                 + "1"
@@ -150,13 +147,15 @@ public void testQueue_retainsItems() {
 
   @Test
   public void testMultiTransactions() {
-    queue.beginTransaction();
+    synchronized (queue.internalQueue) {
+      queue.beginTransactionSync();
+    }
     queue.add(TEST_TOPIC);
 
     // transaction should not be visible from other queue instances yet
     assertThat(initQueue(false).toList()).isEmpty();
 
-    queue.commitTransaction();
+    queue.commitTransactionSync();
     executePendingOperations();
 
     assertThat(initQueue(false).toList()).containsExactly(TEST_TOPIC);