The FacesBridge must follow the requirements in the JSF 2.2 JavaDoc. However, since the Portlet 3.0 API does not have an equivalent to ServletContext.getContextPath() the FacesBridge must rely on the Faces runtime to discover the application context path during initialization.
TCK: Register a javax.faces.event.SystemEventListener that listens for events associated with javax.faces.application.Application. When the event is received, call FacesContext.getCurrentInstance() in order to acquire the "startup" FacesContext instance provided by the Faces runtime. Then call FacesContext.getExternalContext() in order to get the "startup" ExternalContext provided by the Faces runtime. Remember the return value of ExternalContext.getApplicationContextPath(). During a render, assert that the remembered application context path is equal to the value of ExternalContext.getApplicationContextPath().