Verify that PagerSplitter can collect data page by page (#299)

src/test/java/org/gitlab4j/api/PagerSpliteratorTest.java

 package org.gitlab4j.api;
 
 import java.util.Collections;
+import java.util.stream.StreamSupport;
 
 import org.junit.Assert;
 import org.junit.Before;
@@ -9,6 +10,8 @@ import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnitRunner;
 
+import static java.util.Arrays.asList;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -53,4 +56,23 @@ public class PagerSpliteratorTest {
 			assertEquals(NullPointerException.class, e.getClass());
 		}
 	}
+
+	@Test
+	public void shouldAllowToGatherDataPageByPage() {
+		when(pager.hasNext()).thenReturn(true);
+		when(pager.getTotalItems()).thenReturn(12);
+		when(pager.next())
+				.thenReturn(asList(1, 2, 3))
+				.thenReturn(asList(4, 5, 6))
+				.thenReturn(asList(7, 8, 9))
+				.thenReturn(asList(0, 1, 2));
+
+		Integer[] elements = StreamSupport.stream(new PagerSpliterator<Integer>(pager), false)
+				.parallel() // should be ignored
+				.skip(2) // should be ignored
+				.limit(5)
+				.toArray(Integer[]::new);
+
+		assertArrayEquals(new Integer[]{1, 2, 3, 4, 5}, elements);
+	}
 }
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