### Question:
OSMTileEnvoy extends XYZTileEnvoy { @Override protected String buildImageUrlString(DataModelCategory category, ZYXImageKey key) { return OSMUtil.getInstance().buildImageUrlString(category.getSource(), key); } OSMTileEnvoy(Toolbox toolbox); @Override boolean providesDataFor(DataModelCategory category);  }### Answer:
@Test public void testBuildImageUrlString() { EasyMockSupport support = new EasyMockSupport(); Toolbox toolbox = support.createMock(Toolbox.class); support.replayAll(); OSMTileEnvoy envoy = new OSMTileEnvoy(toolbox); DataModelCategory category = new DataModelCategory(ourServer, null, null); ZYXImageKey key = new ZYXImageKey(1, 2, 3, null); String url = envoy.buildImageUrlString(category, key); assertEquals("http: support.verifyAll(); }