Index: trunk/test/unit/org/openstreetmap/josm/actions/DeleteLayerActionTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/actions/DeleteLayerActionTest.java	(revision 18833)
+++ trunk/test/unit/org/openstreetmap/josm/actions/DeleteLayerActionTest.java	(revision 18837)
@@ -5,25 +5,17 @@
 import static org.junit.jupiter.api.Assertions.assertNull;
 
-import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.api.Test;
 import org.openstreetmap.josm.data.osm.DataSet;
 import org.openstreetmap.josm.gui.MainApplication;
 import org.openstreetmap.josm.gui.layer.OsmDataLayer;
-import org.openstreetmap.josm.testutils.JOSMTestRules;
-
-import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import org.openstreetmap.josm.testutils.annotations.Main;
+import org.openstreetmap.josm.testutils.annotations.Projection;
 
 /**
  * Unit tests for class {@link DeleteLayerAction}.
  */
+@Main
+@Projection
 final class DeleteLayerActionTest {
-
-    /**
-     * Setup test.
-     */
-    @RegisterExtension
-    @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
-    public static JOSMTestRules test = new JOSMTestRules().main().projection();
-
     /**
      * Unit test of {@link DeleteLayerAction#actionPerformed}
Index: trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerActionTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerActionTest.java	(revision 18837)
+++ trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerActionTest.java	(revision 18837)
@@ -0,0 +1,128 @@
+package org.openstreetmap.josm.gui.dialogs.layer;
+
+import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.gui.MainApplication;
+import org.openstreetmap.josm.gui.dialogs.LayerListDialog;
+import org.openstreetmap.josm.gui.layer.Layer;
+import org.openstreetmap.josm.gui.layer.OsmDataLayer;
+import org.openstreetmap.josm.testutils.annotations.Main;
+import org.openstreetmap.josm.testutils.annotations.Projection;
+
+/**
+ * Test class for {@link DeleteLayerAction}
+ */
+@Main
+@Projection
+class DeleteLayerActionTest {
+    private LayerListDialog.LayerListModel model;
+    private DeleteLayerAction deleteLayerAction;
+    private ShowHideLayerAction showHideLayerAction;
+
+    @BeforeEach
+    void setup() {
+        final AtomicInteger counter = new AtomicInteger();
+        final Supplier<OsmDataLayer> layerSupplier = () -> new OsmDataLayer(new DataSet(), "testActiveLayer" + counter.getAndIncrement(), null);
+        for (int i = 0; i < 10; i++) {
+            MainApplication.getLayerManager().addLayer(layerSupplier.get());
+        }
+        final LayerListDialog layerListDialog = LayerListDialog.getInstance();
+        this.model = layerListDialog.getModel();
+        this.deleteLayerAction = layerListDialog.createDeleteLayerAction();
+        this.showHideLayerAction = layerListDialog.createShowHideLayerAction();
+    }
+
+    @Test
+    void testSetActiveLayerOnlyOneVisible0to8() {
+        hideRange(0, 8);
+        assertEquals(9, model.getSelectedLayers().size());
+        assertEquals(1, model.getLayers().stream().filter(Layer::isVisible).count());
+        deleteLayerAction.actionPerformed(null);
+        assertEquals(1, model.getSelectedLayers().size());
+        final Layer layer = assertInstanceOf(OsmDataLayer.class, model.getLayer(0));
+        assertNotNull(layer);
+        assertTrue(layer.isVisible());
+        assertSame(layer, model.getLayerManager().getActiveLayer());
+        assertEquals("testActiveLayer0", layer.getName());
+    }
+
+    @Test
+    void testSetActiveLayerOnlyOneVisible1to9() {
+        hideRange(1, 9);
+        assertEquals(9, model.getSelectedLayers().size());
+        assertEquals(1, model.getLayers().stream().filter(Layer::isVisible).count());
+        deleteLayerAction.actionPerformed(null);
+        assertEquals(1, model.getSelectedLayers().size());
+        final Layer layer = assertInstanceOf(OsmDataLayer.class, model.getLayer(0));
+        assertNotNull(layer);
+        assertTrue(layer.isVisible());
+        assertSame(layer, model.getLayerManager().getActiveLayer());
+        assertEquals("testActiveLayer9", layer.getName());
+    }
+
+    @Test
+    void testRemoveMiddleActiveWithSurroundingHiddenLayers() {
+        hideRange(3, 3);
+        hideRange(5, 5);
+        final Layer toRemove = model.getLayer(4);
+        assertNotNull(toRemove);
+        assertTrue(toRemove.isVisible());
+        assertFalse(Objects.requireNonNull(model.getLayer(3)).isVisible());
+        assertFalse(Objects.requireNonNull(model.getLayer(5)).isVisible());
+        model.getLayerManager().setActiveLayer(toRemove);
+        model.setSelectedLayer(toRemove);
+        deleteLayerAction.actionPerformed(null);
+        assertSame(model.getLayerManager().getActiveLayer(), model.getLayer(5));
+        assertEquals("testActiveLayer3", Objects.requireNonNull(model.getLayer(5)).getName());
+        assertAll(model.getLayers().stream().map(layer -> () -> assertNotSame(toRemove, layer)));
+    }
+
+    @Test
+    void testRemoveTopActiveWithSurroundingHiddenLayers() {
+        hideRange(1, 1);
+        final Layer toRemove = model.getLayer(0);
+        assertNotNull(toRemove);
+        assertTrue(toRemove.isVisible());
+        assertFalse(Objects.requireNonNull(model.getLayer(1)).isVisible());
+        model.getLayerManager().setActiveLayer(toRemove);
+        model.setSelectedLayer(toRemove);
+        deleteLayerAction.actionPerformed(null);
+        assertSame(model.getLayerManager().getActiveLayer(), model.getLayer(1));
+        assertEquals("testActiveLayer7", Objects.requireNonNull(model.getLayer(1)).getName());
+        assertAll(model.getLayers().stream().map(layer -> () -> assertNotSame(toRemove, layer)));
+    }
+
+    @Test
+    void testRemoveBottomActiveWithSurroundingHiddenLayers() {
+        hideRange(8, 8);
+        final Layer toRemove = model.getLayer(9);
+        assertNotNull(toRemove);
+        assertTrue(toRemove.isVisible());
+        assertFalse(Objects.requireNonNull(model.getLayer(8)).isVisible());
+        model.getLayerManager().setActiveLayer(toRemove);
+        model.setSelectedLayer(toRemove);
+        deleteLayerAction.actionPerformed(null);
+        assertSame(model.getLayerManager().getActiveLayer(), model.getLayer(7));
+        assertEquals("testActiveLayer2", Objects.requireNonNull(model.getLayer(7)).getName());
+        assertAll(model.getLayers().stream().map(layer -> () -> assertNotSame(toRemove, layer)));
+    }
+
+    private void hideRange(int start, int end) {
+        model.getSelectionModel().setSelectionInterval(start, end);
+        showHideLayerAction.actionPerformed(null);
+    }
+}