diff -r c91483c86597 -r 5df0a239ebeb vmtest/src/main/java/org/apidesign/bck2brwsr/vmtest/impl/Bck2BrwsrCase.java
--- a/vmtest/src/main/java/org/apidesign/bck2brwsr/vmtest/impl/Bck2BrwsrCase.java	Mon Jan 07 18:27:01 2013 +0100
+++ b/vmtest/src/main/java/org/apidesign/bck2brwsr/vmtest/impl/Bck2BrwsrCase.java	Tue Jan 22 11:59:25 2013 +0100
@@ -20,6 +20,7 @@
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
+import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Map;
@@ -37,21 +38,56 @@
     private final Method m;
     private final Launcher l;
     private final String type;
+    private final boolean fail;
     Object value;
     private static final Map<Class, Object[]> compiled = new WeakHashMap<>();
     private Object inst;
 
-    Bck2BrwsrCase(Method m, String type, Launcher l) {
+    Bck2BrwsrCase(Method m, String type, Launcher l, boolean fail) {
         this.l = l;
         this.m = m;
         this.type = type;
+        this.fail = fail;
     }
 
     @Test(groups = "run")
     public void executeCode() throws Throwable {
         if (l != null) {
             MethodInvocation c = l.invokeMethod(m.getDeclaringClass(), m.getName());
-            value = c.toString();
+            String res = c.toString();
+            value = res;
+            if (fail) {
+                int idx = res.indexOf(':');
+                if (idx >= 0) {
+                    Class<? extends Throwable> thrwbl = null;
+                    try {
+                        Class<?> exCls = Class.forName(res.substring(0, idx));
+                        if (Throwable.class.isAssignableFrom(exCls)) {
+                            thrwbl = exCls.asSubclass(Throwable.class);
+                        }
+                    } catch (Exception ex) {
+                        // ignore
+                    }
+                    if (thrwbl != null) {
+                        Throwable t = null;
+                        try {
+                            for (Constructor<?> cnstr : thrwbl.getConstructors()) {
+                                if (cnstr.getParameterTypes().length == 1 && cnstr.getParameterTypes()[0].isAssignableFrom(String.class)) {
+                                    t = (Throwable) cnstr.newInstance(res.substring(idx + 1));
+                                    break;
+                                }
+                            }
+                        } catch (Throwable ex) {
+                            t = thrwbl.newInstance().initCause(ex);
+                        }
+                        if (t == null) {
+                            t = thrwbl.newInstance().initCause(new Exception(res.substring(idx)));
+                        }
+                        throw t;
+                    }
+                    throw new AssertionError(res);
+                }
+            }
         } else {
             try {
                 value = m.invoke(m.getDeclaringClass().newInstance());