[NTP Snippets] Refresh the displayed snippets less frequently

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

Index: chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java
diff --git a/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java b/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java
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+++ b/chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java
@@ -0,0 +1,147 @@
+// Copyright 2016 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.ntp.cards;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+
+import org.chromium.base.BaseChromiumApplication;
+import org.chromium.base.test.util.Feature;
+import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge.SnippetsObserver;
+import org.chromium.chrome.browser.tab.TabObserver;
+import org.chromium.testing.local.LocalRobolectricTestRunner;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+import org.robolectric.annotation.Config;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ * Unit tests for {@link NewTabPageAdapter}.
+ */
+@RunWith(LocalRobolectricTestRunner.class)
+@Config(manifest = Config.NONE, application = BaseChromiumApplication.class)
+public class NewTabPageAdapterTest {
+
+    private NewTabPageManager mNewTabPageManager;
+    private SnippetsObserver mSnippetsObserver;
+    private TabObserver mTabObserver;
+
+    @Before
+    public void setUp() {
+        mNewTabPageManager = mock(NewTabPageManager.class);
+        mSnippetsObserver = null;
+        mTabObserver = null;
+
+        // Intercept the observers so that we can mock invocations.
+        doAnswer(new Answer<Void>() {
+            @Override
+            public Void answer(InvocationOnMock invocation) throws Throwable {
+                mSnippetsObserver = invocation.getArgumentAt(0, SnippetsObserver.class);
+                return null;
+            }}).when(mNewTabPageManager).setSnippetsObserver(any(SnippetsObserver.class));
+
+        doAnswer(new Answer<Void>() {
+            @Override
+            public Void answer(InvocationOnMock invocation) throws Throwable {
+                mTabObserver = invocation.getArgumentAt(0, TabObserver.class);
+                return null;
+            }}).when(mNewTabPageManager).addTabObserver(any(TabObserver.class));
+    }
+
+    /**
+     * Tests the content of the adapter under standard conditions: on start and after a snippet
+     * fetch.
+     */
+    @Test
+    @Feature({"Ntp"})
+    public void testSnippetLoading() {
+        NewTabPageAdapter ntpa = new NewTabPageAdapter(mNewTabPageManager, null);
+        assertEquals(1, ntpa.getItemCount());
+        assertEquals(NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD, ntpa.getItemViewType(0));
+
+        List<SnippetArticle> snippets = Arrays.asList(new SnippetArticle[] {
+                new SnippetArticle("title1", "pub1", "txt1", "https://site.com/url1", null, 0, 0),
+                new SnippetArticle("title2", "pub2", "txt2", "https://site.com/url2", null, 0, 0),
+                new SnippetArticle("title3", "pub3", "txt3", "https://site.com/url3", null, 0, 0)});
+        mSnippetsObserver.onSnippetsReceived(snippets);
+
+        List<NewTabPageListItem> loadedItems = ntpa.getItemsForTesting();
+        assertEquals(NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD, ntpa.getItemViewType(0));
+        assertEquals(NewTabPageListItem.VIEW_TYPE_HEADER, ntpa.getItemViewType(1));
+        assertEquals(snippets, loadedItems.subList(2, loadedItems.size()));
+        assertNull(mSnippetsObserver);
+    }
+
+    /**
+     * Tests that the adapter keeps listening for snippet updates if it didn't get anything from
+     * a previous fetch.
+     */
+    @Test
+    @Feature({"Ntp"})
+    public void testSnippetLoadingInitiallyEmpty() {
+        NewTabPageAdapter ntpa = new NewTabPageAdapter(mNewTabPageManager, null);
+
+        // If we don't get anything, we should still have the above-the-fold item present.
+        mSnippetsObserver.onSnippetsReceived(new ArrayList<SnippetArticle>());
+        assertEquals(1, ntpa.getItemCount());
+        assertEquals(NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD, ntpa.getItemViewType(0));
+        assertNotNull(mSnippetsObserver);
+
+        // We should load new snippets when we get notified about them.
+        List<SnippetArticle> snippets = Arrays.asList(new SnippetArticle[] {
+                new SnippetArticle("title1", "pub1", "txt1", "https://site.com/url1", null, 0, 0),
+                new SnippetArticle("title2", "pub2", "txt2", "https://site.com/url2", null, 0, 0)});
+        mSnippetsObserver.onSnippetsReceived(snippets);
+        List<NewTabPageListItem> loadedItems = ntpa.getItemsForTesting();
+        assertEquals(NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD, ntpa.getItemViewType(0));
+        assertEquals(NewTabPageListItem.VIEW_TYPE_HEADER, ntpa.getItemViewType(1));
+        assertEquals(snippets, loadedItems.subList(2, loadedItems.size()));
+        assertNull(mSnippetsObserver);
+    }
+
+    /**
+     * Tests the behavior on multiple loads. The snippet list should contain only the new ones.
+     */
+    @Test
+    @Feature({"Ntp"})
+    public void testSnippetMultipleLoads() {
+        NewTabPageAdapter ntpa = new NewTabPageAdapter(mNewTabPageManager, null);
+
+        List<SnippetArticle> snippets = Arrays.asList(new SnippetArticle[] {
+                new SnippetArticle("title1", "pub1", "txt1", "https://site.com/url1", null, 0, 0),
+                new SnippetArticle("title2", "pub2", "txt2", "https://site.com/url2", null, 0, 0)});
+        mSnippetsObserver.onSnippetsReceived(snippets);
+
+        // Successfull load, so we should have stopped listening to snippet changes
+        assertNull(mSnippetsObserver);
+
+        // We should be listening to tab events though, and use it to request changes.
+        mTabObserver.onShown(null);
+        assertNotNull(mSnippetsObserver);
+
+        snippets = Arrays.asList(new SnippetArticle[] {
+                new SnippetArticle("title2", "pub2", "txt2", "https://site.com/url2", null, 0, 0),
+                new SnippetArticle("title3", "pub3", "txt3", "https://site.com/url3", null, 0, 0)});
+        mSnippetsObserver.onSnippetsReceived(snippets);
+
+        List<NewTabPageListItem> loadedItems = ntpa.getItemsForTesting();
+        assertEquals(NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD, ntpa.getItemViewType(0));
+        assertEquals(NewTabPageListItem.VIEW_TYPE_HEADER, ntpa.getItemViewType(1));
+        assertEquals(snippets, loadedItems.subList(2, loadedItems.size()));
+    }
+}