Add test for search paging

extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/search/YoutubeSearchPagingTest.java

@@ -0,0 +1,78 @@
+package org.schabi.newpipe.extractor.services.youtube.search;
+
+import static java.util.Collections.singletonList;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.schabi.newpipe.extractor.ServiceList.YouTube;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.schabi.newpipe.DownloaderTestImpl;
+import org.schabi.newpipe.extractor.InfoItem;
+import org.schabi.newpipe.extractor.ListExtractor;
+import org.schabi.newpipe.extractor.NewPipe;
+import org.schabi.newpipe.extractor.services.youtube.extractors.YoutubeSearchExtractor;
+import org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeSearchQueryHandlerFactory;
+
+public class YoutubeSearchPagingTest {
+    private static ListExtractor.InfoItemsPage<InfoItem> page1;
+    private static ListExtractor.InfoItemsPage<InfoItem> page2;
+    private static Set<String> urlList1;
+    private static Set<String> urlList2;
+
+    @BeforeClass
+    public static void setUpClass() throws Exception {
+        NewPipe.init(DownloaderTestImpl.getInstance());
+
+        YoutubeSearchExtractor extractor = (YoutubeSearchExtractor) YouTube.getSearchExtractor("cirque du soleil",
+                singletonList(YoutubeSearchQueryHandlerFactory.VIDEOS), null);
+
+        extractor.fetchPage();
+        page1 = extractor.getInitialPage();
+        urlList1 = extractUrls(page1.getItems());
+        assertEquals("page with items loaded", 20, page1.getItems().size());
+        assertEquals("distinct videos", 20, urlList1.size());
+
+        assertTrue("has more page", page1.hasNextPage());
+        assertNotNull("has next page url", page1.getNextPageUrl());
+        page2 = extractor.getPage(page1.getNextPageUrl());
+        urlList2 = extractUrls(page2.getItems());
+    }
+
+    private static Set<String> extractUrls(List<InfoItem> list) {
+        Set<String> result = new HashSet<>();
+        for (InfoItem item : list) {
+            result.add(item.getUrl());
+        }
+        return result;
+    }
+
+    @Test
+    public void firstPageOk() {
+        assertEquals("page with items loaded", 20, page1.getItems().size());
+        assertEquals("distinct videos", 20, urlList1.size());
+    }
+
+    @Test
+    public void secondPageLength() {
+        assertEquals("one page", 20, page2.getItems().size());
+    }
+
+    @Test
+    public void secondPageUniqueVideos() {
+        assertEquals("distinct videos", 20, urlList2.size());
+    }
+
+    @Test
+    public void noRepeatingVideosInPages() {
+        Set<String> intersection = new HashSet<>(urlList2);
+        intersection.retainAll(urlList1);
+        assertEquals("empty intersection", 0, intersection.size());
+    }
+
+}