Index: trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/LayerVisibilityActionTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/LayerVisibilityActionTest.java	(revision 18011)
+++ trunk/test/unit/org/openstreetmap/josm/gui/dialogs/layer/LayerVisibilityActionTest.java	(revision 18018)
@@ -6,9 +6,10 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
-import org.junit.jupiter.api.Test;
 import org.openstreetmap.josm.gui.MainApplication;
 import org.openstreetmap.josm.gui.dialogs.LayerListDialog;
 import org.openstreetmap.josm.gui.dialogs.LayerListDialog.LayerListModel;
+import org.openstreetmap.josm.gui.dialogs.layer.LayerVisibilityAction.OpacitySlider;
 import org.openstreetmap.josm.gui.layer.TMSLayer;
 import org.openstreetmap.josm.gui.layer.TMSLayerTest;
@@ -52,12 +53,15 @@
         // now check values
         action.updateValues();
-        assertEquals(1.0, action.opacitySlider.getRealValue(), 1e-15);
-        assertEquals("OpacitySlider [getRealValue()=1.0]", action.opacitySlider.toString());
+        OpacitySlider opacitySlider = action.sliders.stream()
+                .filter(x -> x instanceof OpacitySlider).map(x -> (OpacitySlider) x).findFirst().get();
 
-        action.opacitySlider.setRealValue(.5);
+        assertEquals(1.0, opacitySlider.getRealValue(), 1e-15);
+        assertEquals("OpacitySlider [getRealValue()=1.0]", opacitySlider.toString());
+
+        opacitySlider.setRealValue(.5);
         action.updateValues();
 
-        assertEquals(0.5, action.opacitySlider.getRealValue(), 1e-15);
-        assertEquals("OpacitySlider [getRealValue()=0.5]", action.opacitySlider.toString());
+        assertEquals(0.5, opacitySlider.getRealValue(), 1e-15);
+        assertEquals("OpacitySlider [getRealValue()=0.5]", opacitySlider.toString());
 
         action.setVisibleFlag(false);
@@ -70,6 +74,6 @@
 
         // layer stays visible during adjust
-        action.opacitySlider.slider.setValueIsAdjusting(true);
-        action.opacitySlider.setRealValue(0);
+        opacitySlider.slider.setValueIsAdjusting(true);
+        opacitySlider.setRealValue(0);
         assertEquals(0, layer.getOpacity(), 1e-15);
         layer.setOpacity(.1); // to make layer.isVisible work
@@ -77,6 +81,6 @@
         layer.setOpacity(0);
 
-        action.opacitySlider.slider.setValueIsAdjusting(false);
-        action.opacitySlider.setRealValue(0);
+        opacitySlider.slider.setValueIsAdjusting(false);
+        opacitySlider.setRealValue(0);
         assertEquals(0, layer.getOpacity(), 1e-15);
         layer.setOpacity(.1); // to make layer.isVisible work
@@ -88,5 +92,5 @@
         action.setVisibleFlag(true);
         action.updateValues();
-        assertEquals(1.0, action.opacitySlider.getRealValue(), 1e-15);
+        assertEquals(1.0, opacitySlider.getRealValue(), 1e-15);
         assertEquals(1.0, layer.getOpacity(), 1e-15);
     }