Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put(ActionContext.PARAMETERS, params);
ctx.put(ActionContext.SESSION, session);
ac = new ActionContext(ctx);
Action action = new SimpleFooAction();
mai = new MockActionInvocation();
((MockActionInvocation) mai).setAction(action);
((MockActionInvocation) mai).setInvocationContext(ac);
}