Major Description
FormTester (BaseWicketTester.executeAjaxEvent[component,event]) submits also buttons that are hidden (isVisible=false) resulting in exception.
I am trying to ajax-click the visible button, but the formTester arranges even the hidden button to be submitted.. the form processing assumes the hidden button is now the submitting button.. and it is hidden, so an exception is thrown:
org.apache.wicket.WicketRuntimeException: Submit Button hiddenButton (path=form:hiddenButton) is not visible
at org.apache.wicket.markup.html.form.Form$2.component(Form.java:604)
at org.apache.wicket.MarkupContainer.visitChildren(MarkupContainer.java:859)
at org.apache.wicket.MarkupContainer.visitChildren(MarkupContainer.java:874)
at org.apache.wicket.markup.html.form.Form.findSubmittingButton(Form.java:588)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:852)
at org.apache.wicket.ajax.form.AjaxFormSubmitBehavior.onEvent(AjaxFormSubmitBehavior.java:132)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:166)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:299)
at org.apache.wicket.util.tester.BaseWicketTester.executeAjaxEvent(BaseWicketTester.java:1170)
at org.apache.wicket.util.tester.BaseWicketTester.executeAjaxEvent(BaseWicketTester.java:1080)
at com.mycompany.TestHomePage.testAjaxSubmitWhileAnotherButtonIsNotVisible(TestHomePage.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at junit.framework.TestCase.runTest(TestCase.java:164)
at junit.framework.TestCase.runBare(TestCase.java:130)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:120)
at junit.framework.TestSuite.runTest(TestSuite.java:230)
at junit.framework.TestSuite.run(TestSuite.java:225)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
I would assume this is an easy fix to the BaseWicketTester.executeAjaxEvent[component,event]) method where it visits the form components...
An invasive workaround: Just set your hidden button temporarily visible (from within your wickettest) while executing the ajax event 
