Remove mocks and elaborate on comments.

server/src/main/java/org/apache/druid/segment/loading/SegmentLocalCacheManager.java

@@ -126,7 +126,7 @@ public SegmentLocalCacheManager(
       );
     }
 
-    if (this.config.getNumThreadsToLoadSegmentsIntoPageCacheOnDownload() > 0) {
+    if (config.getNumThreadsToLoadSegmentsIntoPageCacheOnDownload() > 0) {
       loadOnDownloadExec = Executors.newFixedThreadPool(
           config.getNumThreadsToLoadSegmentsIntoPageCacheOnDownload(),
           Execs.makeThreadFactory("LoadSegmentsIntoPageCacheOnDownload-%s")
@@ -148,11 +148,11 @@ public List<DataSegment> getCachedSegments() throws IOException
           "canHandleSegments() is false. getCachedSegments() must be invoked only when canHandleSegments() returns true."
       );
     }
-    final File baseDir = getInfoDir();
-    FileUtils.mkdirp(baseDir);
+    final File infoDir = getEffectiveInfoDir();
+    FileUtils.mkdirp(infoDir);
 
     final List<DataSegment> cachedSegments = new ArrayList<>();
-    final File[] segmentsToLoad = baseDir.listFiles();
+    final File[] segmentsToLoad = infoDir.listFiles();
 
     int ignored = 0;
 
@@ -173,7 +173,7 @@ public List<DataSegment> getCachedSegments() throws IOException
         }
       }
       catch (Exception e) {
-        log.makeAlert(e, "Failed to load segment from segmentInfo file")
+        log.makeAlert(e, "Failed to load segment from segment cache file.")
            .addData("file", file)
            .emit();
       }
@@ -191,8 +191,7 @@ public List<DataSegment> getCachedSegments() throws IOException
   @Override
   public void storeInfoFile(DataSegment segment) throws IOException
   {
-    final File infoDir = getInfoDir();
-    final File segmentInfoCacheFile = new File(infoDir, segment.getId().toString());
+    final File segmentInfoCacheFile = new File(getEffectiveInfoDir(), segment.getId().toString());
     if (!segmentInfoCacheFile.exists()) {
       jsonMapper.writeValue(segmentInfoCacheFile, segment);
     }
@@ -201,7 +200,7 @@ public void storeInfoFile(DataSegment segment) throws IOException
   @Override
   public void removeInfoFile(DataSegment segment)
   {
-    final File segmentInfoCacheFile = new File(getInfoDir(), segment.getId().toString());
+    final File segmentInfoCacheFile = new File(getEffectiveInfoDir(), segment.getId().toString());
     if (!segmentInfoCacheFile.delete()) {
       log.warn("Unable to delete cache file[%s] for segment[%s].", segmentInfoCacheFile, segment.getId());
     }
@@ -248,7 +247,19 @@ private SegmentizerFactory getSegmentFactory(final File segmentFiles) throws Seg
     return factory;
   }
 
-  private File getInfoDir()
+  /**
+   * Determines and returns the effective segment info directory based on the configuration settings.
+   * The directory is selected based on the following configurations injected into this class:
+   * <ul>
+   *   <li>{@link SegmentLoaderConfig#infoDir} - If this is set, it is used as the info directory.</li>
+   *   <li>{@link SegmentLoaderConfig#locations} - If the info directory is not set, the first location from this list is used.</li>
+   *   <li>List of {@link StorageLocation}s injected - If both the info directory and locations list are not set, the
+   *   first storage location is used.</li>
+   * </ul>
+   *
+   * @throws DruidException if none of the configurations are set, and the info directory cannot be determined.
+   */
+  private File getEffectiveInfoDir()
   {
     final File infoDir;
     if (config.getInfoDir() != null) {

server/src/test/java/org/apache/druid/server/coordination/SegmentLoadDropHandlerCacheTest.java

@@ -41,19 +41,14 @@
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
-import org.mockito.ArgumentCaptor;
-import org.mockito.Mockito;
 
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import static org.mockito.ArgumentMatchers.any;
-
 /**
  * Similar to {@link SegmentLoadDropHandlerTest}. This class includes tests that cover the
  * storage location layer as well.
@@ -65,7 +60,7 @@ public class SegmentLoadDropHandlerCacheTest
   @Rule
   public TemporaryFolder temporaryFolder = new TemporaryFolder();
   private SegmentLoadDropHandler loadDropHandler;
-  private DataSegmentAnnouncer segmentAnnouncer;
+  private TestDataSegmentAnnouncer segmentAnnouncer;
   private DataSegmentServerAnnouncer serverAnnouncer;
   private SegmentManager segmentManager;
   private SegmentLoaderConfig loaderConfig;
@@ -108,7 +103,7 @@ public List<StorageLocationConfig> getLocations()
         objectMapper
     );
     segmentManager = new SegmentManager(cacheManager);
-    segmentAnnouncer = Mockito.mock(DataSegmentAnnouncer.class);
+    segmentAnnouncer = new TestDataSegmentAnnouncer();
 
     observedAnnouncedServerCount = new AtomicInteger(0);
     serverAnnouncer = new DataSegmentServerAnnouncer()
@@ -205,24 +200,17 @@ public void testLoadLocalCache() throws IOException, SegmentLoadingException
     Assert.assertEquals(1, observedAnnouncedServerCount.get());
 
     // Verify the expected announcements
-    ArgumentCaptor<Iterable<DataSegment>> argCaptor = ArgumentCaptor.forClass(Iterable.class);
-    Mockito.verify(segmentAnnouncer).announceSegments(argCaptor.capture());
-    List<DataSegment> announcedSegments = new ArrayList<>();
-    argCaptor.getValue().forEach(announcedSegments::add);
-    announcedSegments.sort(Comparator.comparing(DataSegment::getVersion));
-    Assert.assertEquals(expectedSegments, announcedSegments);
-
-    // make sure adding segments beyond allowed size fails
-    Mockito.reset(segmentAnnouncer);
+    Assert.assertTrue(segmentAnnouncer.getObservedSegments().containsAll(expectedSegments));
+
+    // Make sure adding segments beyond allowed size fails
     DataSegment newSegment = makeSegment("test", "new-segment");
     loadDropHandler.addSegment(newSegment, null);
-    Mockito.verify(segmentAnnouncer, Mockito.never()).announceSegment(any());
-    Mockito.verify(segmentAnnouncer, Mockito.never()).announceSegments(any());
+    Assert.assertFalse(segmentAnnouncer.getObservedSegments().contains(newSegment));
 
-    // clearing some segment should allow for new segments
+    // Clearing some segment should allow for new segments
     loadDropHandler.removeSegment(expectedSegments.get(0), null, false);
     loadDropHandler.addSegment(newSegment, null);
-    Mockito.verify(segmentAnnouncer).announceSegment(newSegment);
+    Assert.assertTrue(segmentAnnouncer.getObservedSegments().contains(newSegment));
 
     loadDropHandler.stop();
     Assert.assertEquals(0, observedAnnouncedServerCount.get());