diff -r 06e7a74c72cf -r 265edcee24ed launcher/fx/src/main/java/org/apidesign/bck2brwsr/launcher/BaseHTTPLauncher.java
--- a/launcher/fx/src/main/java/org/apidesign/bck2brwsr/launcher/BaseHTTPLauncher.java	Tue May 28 21:49:38 2013 +0200
+++ b/launcher/fx/src/main/java/org/apidesign/bck2brwsr/launcher/BaseHTTPLauncher.java	Fri Jun 21 22:34:09 2013 +0200
@@ -177,20 +177,19 @@
         server = initServer(".", true);
         final ServerConfiguration conf = server.getServerConfiguration();
         
-        class DynamicResourceHandler extends HttpHandler {
+        class DynamicResourceHandler extends HttpHandler implements InvocationContext.RegisterResource {
             private final InvocationContext ic;
             public DynamicResourceHandler(InvocationContext ic) {
-                if (ic == null || ic.resources.isEmpty()) {
-                    throw new NullPointerException();
-                }
                 this.ic = ic;
                 for (Resource r : ic.resources) {
                     conf.addHttpHandler(this, r.httpPath);
                 }
+                InvocationContext.register(this);
             }
 
             public void close() {
                 conf.removeHttpHandler(this);
+                InvocationContext.register(null);
             }
             
             @Override
@@ -231,6 +230,15 @@
                     }
                 }
             }
+
+            @Override
+            public URI registerResource(Resource r) {
+                if (!ic.resources.contains(r)) {
+                    ic.resources.add(r);
+                    conf.addHttpHandler(this, r.httpPath);
+                }
+                return pageURL(server, r.httpPath);
+            }
         }
         
         conf.addHttpHandler(new Page(resources, harnessResource()), "/execute");
@@ -286,9 +294,7 @@
                     return;
                 }
                 
-                if (!mi.resources.isEmpty()) {
-                    prev = new DynamicResourceHandler(mi);
-                }
+                prev = new DynamicResourceHandler(mi);
                 
                 cases.add(mi);
                 final String cn = mi.clazz.getName();
@@ -381,10 +387,7 @@
 
     private Object[] launchServerAndBrwsr(HttpServer server, final String page) throws IOException, URISyntaxException, InterruptedException {
         server.start();
-        NetworkListener listener = server.getListeners().iterator().next();
-        int port = listener.getPort();
-        
-        URI uri = new URI("http://localhost:" + port + page);
+        URI uri = pageURL(server, page);
         return showBrwsr(uri);
     }
     private static String toUTF8(String value) throws UnsupportedEncodingException {
@@ -496,6 +499,16 @@
     abstract void generateBck2BrwsrJS(StringBuilder sb, Res loader) throws IOException;
     abstract String harnessResource();
 
+    private static URI pageURL(HttpServer server, final String page) {
+        NetworkListener listener = server.getListeners().iterator().next();
+        int port = listener.getPort();
+        try {
+            return new URI("http://localhost:" + port + page);
+        } catch (URISyntaxException ex) {
+            throw new IllegalStateException(ex);
+        }
+    }
+
     class Res {
         public InputStream get(String resource) throws IOException {
             URL u = null;