Proteus Wizard: state vs. form_state

I created a wizard (see below) and added a test scenario for it. The wizard shows a form, imports some data (state import_) and shows a result summary (state result).

Now this simple test fails:

   >>> importer = Wizard('importwizard.tests.import.test')
   >>> importer.execute('import_')
   >>> assert importer.state == 'result'

importer.state is still import_, while I would expect it to be result.
Anyhow there is importer.from_state, which contains the expected value result.

Why is the state not result, too? Is this a bug to report?

    class MyImportWizard(Wizard):
       '''Stripped down example wizard'''
        __name__ = 'importwizard.tests.import.test'
        start = StateView(…, …, [
                Button("Import", 'import_', 'tryton-ok'),
        import_ = StateTransition()
        result = StateView(…, …, [
                Button("Close", 'end', 'tryton-close'),

        def transition_import_(self):
            return 'result'