Rewrite addToHistory test without using reflection

Author: imericxu

app/src/test/java/org/schabi/newpipe/player/playqueue/PlayQueueTest.java

@@ -8,17 +8,17 @@
 import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 import org.schabi.newpipe.extractor.stream.StreamType;
 
-import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 
 @SuppressWarnings("checkstyle:HideUtilityClassConstructor")
@@ -53,9 +53,11 @@ public static class SetIndexTests {
 
         @Before
         public void setup() {
-            nonEmptyQueue = spy(makePlayQueue(
-                    0, Collections.nCopies(SIZE, mock(PlayQueueItem.class))
-            ));
+            final List<PlayQueueItem> streams = new ArrayList<>(5);
+            for (int i = 0; i < 5; ++i) {
+                streams.add(makeItemWithUrl("URL_" + i));
+            }
+            nonEmptyQueue = spy(makePlayQueue(0, streams));
             emptyQueue = spy(makePlayQueue(0, new ArrayList<>()));
         }
 
@@ -112,30 +114,14 @@ public void indexZero() {
             assertEquals(0, emptyQueue.getIndex());
         }
 
-        @SuppressWarnings("unchecked")
         @Test
-        public void addToHistory() throws NoSuchFieldException, IllegalAccessException {
-            final Field field;
-            field = PlayQueue.class.getDeclaredField("history");
-            field.setAccessible(true);
-            List<PlayQueueItem> history;
-
-            /*
-            history's size is currently 1. 0 is the also the current index, so history should not
-            be affected.
-             */
+        public void addToHistory() {
             nonEmptyQueue.setIndex(0);
-            history = (List<PlayQueueItem>) Objects.requireNonNull(
-                    field.get(nonEmptyQueue)
-            );
-            assertEquals(1, history.size());
+            assertFalse(nonEmptyQueue.previous());
 
-            // Index 3 != 0, so the second history element should be the item at streams[3]
             nonEmptyQueue.setIndex(3);
-            history = (List<PlayQueueItem>) Objects.requireNonNull(
-                    field.get(nonEmptyQueue)
-            );
-            assertEquals(nonEmptyQueue.getItem(3), history.get(1));
+            assertTrue(nonEmptyQueue.previous());
+            assertEquals("URL_0", Objects.requireNonNull(nonEmptyQueue.getItem()).getUrl());
         }
     }