@Test
public void testTextBoxValueChangeHandler() {

    final TextBox textBox = mock(TextBox.class);
    final String textBoxValue = "123";
    doReturn(textBoxValue).when(textBox).getValue();
    factory.initTextBoxByRuleAttribute(textBox, ruleAttribute);
    verify(textBox).addValueChangeHandler(valueChangeHandlerArgumentCaptor.capture());
    valueChangeHandlerArgumentCaptor.getValue().onValueChange(null);
    verify(ruleAttribute).setValue(textBoxValue);
}