public T multiply(BigDecimal multiplier) {
        return create(value.multiply(multiplier));
    }
@Test
    void testMutiplyNegativeInteger() {
        final Resource resource = new TestResource(0.3);
        final int by = -2;
        assertThatThrownBy(() -> resource.multiply(by))
                .isInstanceOf(IllegalArgumentException.class);
    }