NumericIntegerTextBox extends AbstractRestrictedEntryTextBox { @Override protected String makeValidValue(String value) { return "0"; } NumericIntegerTextBox();  NumericIntegerTextBox(final boolean allowEmptyValue); @Override boolean isValidValue(final String value,
                                final boolean isOnFocusLost);  }
@Test public void testDefaultValue() { Assertions.assertThat(numericIntegerTextBox.makeValidValue("")).isEqualTo("0"); Assertions.assertThat(numericIntegerTextBox.makeValidValue("123")).isEqualTo("0"); Assertions.assertThat(numericIntegerTextBox.makeValidValue("-123")).isEqualTo("0"); Assertions.assertThat(numericIntegerTextBox.makeValidValue("abcd")).isEqualTo("0"); }