[Android O] Only delete legacy notification channels on upgrade

chrome/android/junit/src/org/chromium/chrome/browser/notifications/ChannelsInitializerTest.java

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.notifications;
 
 import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.hamcrest.Matchers.empty;
+import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertThat;
 
 import android.app.NotificationManager;
 
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.BlockJUnit4ClassRunner;
 
 import org.chromium.chrome.test.util.browser.notifications.MockNotificationManagerProxy;
 
 /**
  * Unit tests for ChannelsInitializer.
  */
 @RunWith(BlockJUnit4ClassRunner.class)
 public class ChannelsInitializerTest {
     private ChannelsInitializer mChannelsInitializer;
     private MockNotificationManagerProxy mMockNotificationManager;
 
     @Before
     public void setUp() throws Exception {
         mMockNotificationManager = new MockNotificationManagerProxy();
         mChannelsInitializer =
                 new ChannelsInitializer(mMockNotificationManager, new ChannelDefinitions());
     }
 
     @Test
+    public void testDeleteLegacyChannels_noopOnCurrentDefinitions() throws Exception {
+        assertThat(mMockNotificationManager.getNotificationChannelIds(), is(empty()));
+
+        mChannelsInitializer.deleteLegacyChannels();
+        assertThat(mMockNotificationManager.getNotificationChannelIds(), is(empty()));
+
+        mChannelsInitializer.initializeStartupChannels();
+        assertThat(mMockNotificationManager.getNotificationChannelIds(), is(not(empty())));
+
+        int nChannels = mMockNotificationManager.getNotificationChannelIds().size();
+        mChannelsInitializer.deleteLegacyChannels();
+        assertThat(mMockNotificationManager.getNotificationChannelIds(), hasSize(nChannels));
+    }
+
+    @Test
     public void testInitializeStartupChannels() throws Exception {
         mChannelsInitializer.initializeStartupChannels();
         assertThat(mMockNotificationManager.getNotificationChannelIds(),
                 containsInAnyOrder(ChannelDefinitions.CHANNEL_ID_BROWSER,
                         ChannelDefinitions.CHANNEL_ID_DOWNLOADS,
                         ChannelDefinitions.CHANNEL_ID_INCOGNITO,
                         ChannelDefinitions.CHANNEL_ID_SITES, ChannelDefinitions.CHANNEL_ID_MEDIA));
     }
 
     @Test
@@ skipping 97 matching lines @@
                 is(org.chromium.chrome.R.string.notification_category_group_general));
     }
 
     @Test
     public void testEnsureInitialized_multipleCalls() throws Exception {
         mChannelsInitializer.ensureInitialized(ChannelDefinitions.CHANNEL_ID_SITES);
         mChannelsInitializer.ensureInitialized(ChannelDefinitions.CHANNEL_ID_BROWSER);
         assertThat(mMockNotificationManager.getChannels().size(), is(2));
     }
 }