[HUDI-2115] FileSlices in the filegroup is not descending by timestamp (#3206)

hudi-common/src/test/java/org/apache/hudi/common/model/TestHoodieFileGroup.java

@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hudi.common.model;
+
+import org.apache.hudi.common.testutils.MockHoodieTimeline;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TestHoodieFileGroup {
+
+  @Test
+  public void testCommittedFileSlices() {
+    // "000" is archived
+    Stream<String> completed = Arrays.asList("001").stream();
+    Stream<String> inflight = Arrays.asList("002").stream();
+    MockHoodieTimeline activeTimeline = new MockHoodieTimeline(completed, inflight);
+    HoodieFileGroup fileGroup = new HoodieFileGroup("", "data",
+        activeTimeline.getCommitsTimeline().filterCompletedInstants());
+    for (int i = 0; i < 3; i++) {
+      HoodieBaseFile baseFile = new HoodieBaseFile("data_1_00" + i);
+      fileGroup.addBaseFile(baseFile);
+    }
+    assertEquals(2, fileGroup.getAllFileSlices().count());
+    assertTrue(!fileGroup.getAllFileSlices().anyMatch(s -> s.getBaseInstantTime().equals("002")));
+    assertEquals(3, fileGroup.getAllFileSlicesIncludingInflight().count());
+    assertTrue(fileGroup.getLatestFileSlice().get().getBaseInstantTime().equals("001"));
+    assertTrue((new HoodieFileGroup(fileGroup)).getLatestFileSlice().get().getBaseInstantTime().equals("001"));
+  }
+}