HttpUnit和jQuery：EcmaError

org.mozilla.javascript.EcmaError: TypeError: Cannot find function createElement in object [object Document]. (httpunit#916)
    at org.mozilla.javascript.ScriptRuntime.constructError(ScriptRuntime.java:3654)
    at org.mozilla.javascript.ScriptRuntime.constructError(ScriptRuntime.java:3632)
    at org.mozilla.javascript.ScriptRuntime.typeError(ScriptRuntime.java:3660)
    at org.mozilla.javascript.ScriptRuntime.typeError2(ScriptRuntime.java:3679)
    at org.mozilla.javascript.ScriptRuntime.notFunctionError(ScriptRuntime.java:3743)
    at org.mozilla.javascript.ScriptRuntime.getPropFunctionAndThisHelper(ScriptRuntime.java:2247)
    at org.mozilla.javascript.ScriptRuntime.getPropFunctionAndThis(ScriptRuntime.java:2214)
    at org.mozilla.javascript.Interpreter.interpretLoop(Interpreter.java:3143)
    at script(httpunit:916)
    at script(httpunit:912)
    at script(httpunit:15)
    at org.mozilla.javascript.Interpreter.interpret(Interpreter.java:2487)
    at org.mozilla.javascript.InterpretedFunction.call(InterpretedFunction.java:164)
    at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:398)
    at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3065)
    at org.mozilla.javascript.InterpretedFunction.exec(InterpretedFunction.java:175)
    at org.mozilla.javascript.Context.evaluateString(Context.java:1104)
    at com.meterware.httpunit.javascript.ScriptingEngineImpl.runScript(ScriptingEngineImpl.java:92)
    at com.meterware.httpunit.scripting.ScriptableDelegate.runScript(ScriptableDelegate.java:88)
    at com.meterware.httpunit.ParsedHTML.interpretScriptElement(ParsedHTML.java:364)
    at com.meterware.httpunit.ParsedHTML$ScriptFactory.recordElement(ParsedHTML.java:533)
    at com.meterware.httpunit.ParsedHTML$2.processElement(ParsedHTML.java:744)
    at com.meterware.httpunit.NodeUtils$PreOrderTraversal.perform(NodeUtils.java:241)
    at com.meterware.httpunit.ParsedHTML.loadElements(ParsedHTML.java:760)
    at com.meterware.httpunit.ParsedHTML.getFrames(ParsedHTML.java:1101)
    at com.meterware.httpunit.WebResponse.getFrames(WebResponse.java:1285)
    at com.meterware.httpunit.WebResponse.getFrameRequests(WebResponse.java:1024)
    at com.meterware.httpunit.FrameHolder.updateFrames(FrameHolder.java:179)
    at com.meterware.httpunit.WebWindow.updateFrameContents(WebWindow.java:315)
    at com.meterware.httpunit.WebClient.updateFrameContents(WebClient.java:526)
    at com.meterware.httpunit.WebWindow.updateWindow(WebWindow.java:201)
    at com.meterware.httpunit.WebWindow.getSubframeResponse(WebWindow.java:183)
    at com.meterware.httpunit.WebWindow.getResponse(WebWindow.java:158)
    at com.meterware.httpunit.WebWindow.sendRequest(WebWindow.java:134)
    at com.meterware.httpunit.WebResponse.submitRequest(WebResponse.java:742)
    at com.meterware.httpunit.dom.DomWindow.submitRequest(DomWindow.java:181)
    at com.meterware.httpunit.dom.HTMLAnchorElementImpl.doClickAction(HTMLAnchorElementImpl.java:183)
    at com.meterware.httpunit.WebLink.click(WebLink.java:96)
    at mycompany.testcase.pages.WelcomePage.goToFilterPage(WelcomePage.java:30)
    at mycompany.testcase.DownloadReportTest.testReportDownload(DownloadReportTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at junit.framework.TestCase.runTest(TestCase.java:168)
    at junit.framework.TestCase.runBare(TestCase.java:134)
    at junit.framework.TestResult$1.protect(TestResult.java:110)
    at junit.framework.TestResult.runProtected(TestResult.java:128)
    at junit.framework.TestResult.run(TestResult.java:113)
    at junit.framework.TestCase.run(TestCase.java:124)
    at junit.framework.TestSuite.runTest(TestSuite.java:243)
    at junit.framework.TestSuite.run(TestSuite.java:238)
    at junit.framework.TestSuite.runTest(TestSuite.java:243)
    at junit.framework.TestSuite.run(TestSuite.java:238)
    at mycompany.App.main(App.java:29)