Index: /trunk/src/org/openstreetmap/josm/gui/layer/imagery/TileCoordinateConverter.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/layer/imagery/TileCoordinateConverter.java	(revision 11909)
+++ /trunk/src/org/openstreetmap/josm/gui/layer/imagery/TileCoordinateConverter.java	(revision 11910)
@@ -6,4 +6,5 @@
 import java.awt.geom.Point2D;
 import java.awt.geom.Rectangle2D;
+import java.util.Objects;
 
 import org.openstreetmap.gui.jmapviewer.Tile;
@@ -35,9 +36,10 @@
      * @param tileSource The tile source to use when converting coordinates.
      * @param settings displacement settings.
+     * @throws NullPointerException if one argument is null
      */
     public TileCoordinateConverter(MapView mapView, TileSource tileSource, TileSourceDisplaySettings settings) {
-        this.mapView = mapView;
-        this.tileSource = tileSource;
-        this.settings = settings;
+        this.mapView = Objects.requireNonNull(mapView, "mapView");
+        this.tileSource = Objects.requireNonNull(tileSource, "tileSource");
+        this.settings = Objects.requireNonNull(settings, "settings");
     }
 
Index: /trunk/test/unit/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayerTest.java
===================================================================
--- /trunk/test/unit/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayerTest.java	(revision 11910)
+++ /trunk/test/unit/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayerTest.java	(revision 11910)
@@ -0,0 +1,217 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.gui.layer;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.awt.Point;
+import java.util.Collection;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.openstreetmap.gui.jmapviewer.Coordinate;
+import org.openstreetmap.gui.jmapviewer.Projected;
+import org.openstreetmap.gui.jmapviewer.Tile;
+import org.openstreetmap.gui.jmapviewer.TileRange;
+import org.openstreetmap.gui.jmapviewer.TileXY;
+import org.openstreetmap.gui.jmapviewer.interfaces.ICoordinate;
+import org.openstreetmap.gui.jmapviewer.interfaces.IProjected;
+import org.openstreetmap.gui.jmapviewer.interfaces.TileCache;
+import org.openstreetmap.gui.jmapviewer.interfaces.TileLoader;
+import org.openstreetmap.gui.jmapviewer.interfaces.TileLoaderListener;
+import org.openstreetmap.gui.jmapviewer.tilesources.AbstractTMSTileSource;
+import org.openstreetmap.gui.jmapviewer.tilesources.TileSourceInfo;
+import org.openstreetmap.josm.data.imagery.ImageryInfo;
+import org.openstreetmap.josm.data.imagery.TileLoaderFactory;
+import org.openstreetmap.josm.gui.layer.imagery.ImageryFilterSettings;
+import org.openstreetmap.josm.testutils.JOSMTestRules;
+
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+
+/**
+ * Test of the base {@link AbstractTileSourceLayer} class
+ */
+public class AbstractTileSourceLayerTest {
+
+    /**
+     * Setup test
+     */
+    @Rule
+    @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
+    public JOSMTestRules test = new JOSMTestRules().platform().projection().commands();
+
+    private static final class TMSTileStubSource extends AbstractTMSTileSource {
+        private TMSTileStubSource() {
+            super(new TileSourceInfo());
+        }
+
+        @Override
+        public double getDistance(double la1, double lo1, double la2, double lo2) {
+            // TODO Auto-generated method stub
+            return 0;
+        }
+
+        @Override
+        public Point latLonToXY(double lat, double lon, int zoom) {
+            // TODO Auto-generated method stub
+            return null;
+        }
+
+        @Override
+        public ICoordinate xyToLatLon(int x, int y, int zoom) {
+            // TODO Auto-generated method stub
+            return null;
+        }
+
+        @Override
+        public TileXY latLonToTileXY(double lat, double lon, int zoom) {
+            return new TileXY(lon / 2, lat / 2);
+        }
+
+        @Override
+        public ICoordinate tileXYToLatLon(int x, int y, int zoom) {
+            return new Coordinate(2*y, 2*x);
+        }
+
+        @Override
+        public IProjected tileXYtoProjected(int x, int y, int zoom) {
+            return new Projected(2*x, 2*y);
+        }
+
+        @Override
+        public TileXY projectedToTileXY(IProjected p, int zoom) {
+            return new TileXY(p.getEast() / 2, p.getNorth() / 2);
+        }
+
+        @Override
+        public boolean isInside(Tile inner, Tile outer) {
+            // TODO Auto-generated method stub
+            return false;
+        }
+
+        @Override
+        public TileRange getCoveringTileRange(Tile tile, int newZoom) {
+            // TODO Auto-generated method stub
+            return null;
+        }
+
+        @Override
+        public String getServerCRS() {
+            return "EPSG:3857";
+        }
+    }
+
+    private static class TileSourceStubLayer extends AbstractTileSourceLayer<AbstractTMSTileSource> {
+
+        TileSourceStubLayer() {
+            super(new ImageryInfo());
+            hookUpMapView();
+        }
+
+        @Override
+        protected TileLoaderFactory getTileLoaderFactory() {
+            return new TileLoaderFactory() {
+                @Override
+                public TileLoader makeTileLoader(TileLoaderListener listener, Map<String, String> headers) {
+                    return null;
+                }
+            };
+        }
+
+        @Override
+        public Collection<String> getNativeProjections() {
+            return null;
+        }
+
+        @Override
+        protected AbstractTMSTileSource getTileSource() {
+            return new TMSTileStubSource();
+        }
+
+        TileCache getTileCache() {
+            return tileCache;
+        }
+    }
+
+    private TileSourceStubLayer testLayer;
+    AtomicBoolean invalidated = new AtomicBoolean();
+
+    /**
+     * Create test layer
+     */
+    @Before
+    public void setUp() {
+        testLayer = new TileSourceStubLayer();
+        testLayer.addInvalidationListener(l -> invalidated.set(true));
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer#filterChanged}
+     */
+    @Test
+    public void testFilterChanged() {
+        try {
+            ImageryFilterSettings filterSettings = new ImageryFilterSettings();
+            filterSettings.addFilterChangeListener(testLayer);
+            assertFalse(invalidated.get());
+            filterSettings.setGamma(0.5);
+            assertTrue(invalidated.get());
+        } finally {
+            invalidated.set(false);
+        }
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer#redraw}
+     */
+    @Test
+    public void testRedraw() {
+        try {
+            assertFalse(invalidated.get());
+            testLayer.redraw();
+            assertTrue(invalidated.get());
+        } finally {
+            invalidated.set(false);
+        }
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer#clearTileCache}
+     */
+    @Test
+    public void testClearTileCache() {
+        testLayer.loadAllTiles(true);
+        assertTrue(testLayer.getTileCache().getTileCount() > 0);
+        testLayer.clearTileCache();
+        assertEquals(0, testLayer.getTileCache().getTileCount());
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer#getAdjustAction}
+     */
+    @Test
+    public void testGetAdjustAction() {
+        assertNotNull(testLayer.getAdjustAction());
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer#getInfoComponent}
+     */
+    @Test
+    public void testGetInfoComponent() {
+        assertNotNull(testLayer.getInfoComponent());
+    }
+
+    /**
+     * Test {@link AbstractTileSourceLayer.TileSourceLayerPopup}
+     */
+    @Test
+    public void testTileSourceLayerPopup() {
+        assertNotNull(testLayer.new TileSourceLayerPopup());
+    }
+}