grails – 如何使用MockFor在HttpBuilder上模拟客户端？

class RunkeeperActivitiesRetrieverService {
    def http = new RESTClient("http://api.runkeeper.com/")

    def getActivities() {
        http.client.clearRequestInterceptors();
        http.client.addRequestInterceptor(new HttpRequestInterceptor() {
            void process(HttpRequest httpRequest,HttpContext httpContext) {
                httpRequest.addHeader('Authorization','Bearer xxxxxxxxxx')
            }
        })
        //Do more with the httpBuilder
    }
}

我在这里找到了一些关于模拟HTTPBuilder主题的帮助：Groovy HTTPBuilder Mocking the Response和一些关于groovy docs中的模拟接口：http://groovy.codehaus.org/Groovy+way+to+implement+interfaces

使用该代码我来到这个测试代码：

def mock = new MockFor(HTTPBuilder)
def impl = [
    addRequestInterceptor : {HttpRequestInterceptor interceptor -> println "hi 4"+interceptor},clearRequestInterceptors : {println "hi 88"}
            ]
def client = impl as HttpClient

mock.demand.getClient {return client}
mock.use{
    service.http = new HTTPBuilder()
    println service.getActivities()
}

不幸的是我对Groovy的了解太有限了,无法解决引发的异常：groovy.lang.MissingMethodException：没有方法签名：$Proxy15.clearRequestInterceptors()适用于参数类型:()值：[]

我在这里错过了什么？