@Override
    protected boolean isNan(Integer number) {
        // NaN never applies here because only types like Float and Double have NaN
        return false;
    }
@Test
    void testIsNan() {
        IntegerSummaryAggregator ag = new IntegerSummaryAggregator();
        // always false for Integer
        assertThat(ag.isNan(-1)).isFalse();
        assertThat(ag.isNan(0)).isFalse();
        assertThat(ag.isNan(23)).isFalse();
        assertThat(ag.isNan(Integer.MAX_VALUE)).isFalse();
        assertThat(ag.isNan(Integer.MIN_VALUE)).isFalse();
        assertThat(ag.isNan(null)).isFalse();
    }