$questiondata = test_question_maker::get_question_data('multichoice', 'single');

$expectedfromform = test_question_maker::get_question_form_data('multichoice', 'single');

$form = new qtype_multichoice_edit_form(...);

$form->set_data(questiondata);

$form->mock_submit(); // I don't think this exists but it could.

$actualfromform = $form->get_data();

$this->assertEquals($expectedfromform, $actualfromform);

save_question($actualfromform);

$actualquestiondata = question_load_questions(array($actualfromform->id));

$this->assertEquals($questiondata, $actualquestiondata);