📰 Fix card style when a neighbour is added or removed

chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java

Index: chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java
diff --git a/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java b/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java
index 3d8b185de739a343c971cea2afe761d28abf95ae..10b29b8cf441d003e047bb02da47471ebe37f13d 100644
--- a/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java
+++ b/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java
@@ -32,6 +32,7 @@
 import org.robolectric.annotation.Config;
 
 import org.chromium.base.Callback;
+import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.test.util.Feature;
 import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.EnableFeatures;
@@ -41,6 +42,7 @@
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
 import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
 import org.chromium.chrome.browser.offlinepages.OfflinePageItem;
+import org.chromium.chrome.browser.suggestions.PartialUpdateId;
 import org.chromium.chrome.browser.suggestions.SuggestionsMetricsReporter;
 import org.chromium.chrome.browser.suggestions.SuggestionsNavigationDelegate;
 import org.chromium.chrome.browser.suggestions.SuggestionsRanker;
@@ -68,6 +70,7 @@
 
     @Before
     public void setUp() {
+        RecordHistogram.disableForTests();
         MockitoAnnotations.initMocks(this);
         mBridge = new FakeOfflinePageBridge();
 
@@ -143,7 +146,6 @@ public void testSetStatusNotification() {
 
         section.setStatus(CategoryStatus.AVAILABLE);
         verify(mParent).onItemRangeRemoved(section, 2, 1);
-        verifyNoMoreInteractions(mParent);
     }
 
     @Test
@@ -557,6 +559,32 @@ public void testSectionDoesNotUpdateOnNewSuggestionsWhenAllSeen() {
         }
     }
 
+    @Test
+    @Feature({"Ntp"})
+    public void testCardIsNotifiedWhenBecomingFirstOrLast() {
+        List<SnippetArticle> suggestions = createDummySuggestions(3, /* categoryId = */ 42);
+        SuggestionsSection section = createSectionWithReloadAction(false);
+        section.setStatus(CategoryStatus.AVAILABLE);
+        section.setSuggestions(suggestions, CategoryStatus.AVAILABLE, /* replaceExisting = */ true);
+
+        // When the first suggestion is removed, the new first should be notified to update its
+        // background.
+        section.removeSuggestionById(suggestions.get(0).mIdWithinCategory);
+        verify(mParent).onItemRangeChanged(section, 2, 1, PartialUpdateId.CARD_BACKGROUND);
+
+        // When the last suggestion is removed, the new last should be notified to update its
+        // background.
+        section.removeSuggestionById(suggestions.get(2).mIdWithinCategory);
+        verify(mParent).onItemRangeChanged(section, 1, 1, PartialUpdateId.CARD_BACKGROUND);
+
+        // When items are added after the last suggestion, it should be notified to update its
+        // background.
+        section.setSuggestions(createDummySuggestions(2, /* categoryId = */ 42, "new"),
+                CategoryStatus.AVAILABLE, /* replaceExisting = */ false);
+        verify(mParent, times(2))
+                .onItemRangeChanged(section, 1, 1, PartialUpdateId.CARD_BACKGROUND);
+    }
+
     private SuggestionsSection createSectionWithSuggestions(List<SnippetArticle> snippets) {
         SuggestionsSection section = createSectionWithReloadAction(true);
         section.setStatus(CategoryStatus.AVAILABLE);