Index: trunk/test/unit/org/openstreetmap/josm/gui/layer/geoimage/ThumbsLoaderTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/layer/geoimage/ThumbsLoaderTest.java	(revision 17856)
+++ trunk/test/unit/org/openstreetmap/josm/gui/layer/geoimage/ThumbsLoaderTest.java	(revision 17856)
@@ -0,0 +1,43 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.gui.layer.geoimage;
+
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.openstreetmap.josm.testutils.JOSMTestRules;
+import org.openstreetmap.josm.tools.StreamUtils;
+
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Unit tests of {@link ThumbsLoader} class.
+ */
+class ThumbsLoaderTest {
+    /**
+     * Setup test.
+     */
+    @RegisterExtension
+    @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
+    public JOSMTestRules test = new JOSMTestRules().main();
+
+    /**
+     * Performance test for {@link ThumbsLoader}
+     * @throws Exception if any error occurs
+     */
+    @Test
+    @Disabled("Set working directory to image folder and run manually")
+    void testPerformance() throws Exception {
+        List<ImageEntry> imageEntries;
+        try (DirectoryStream<Path> stream = Files.newDirectoryStream(Paths.get(".").toAbsolutePath(), "*.{JPG,jpg}")) {
+            imageEntries = StreamUtils.toStream(stream).map(Path::toFile).map(ImageEntry::new).collect(Collectors.toList());
+        }
+        new ThumbsLoader(imageEntries).run();
+    }
+
+}