@Override
    public RangeBoundary getLowBoundary() {
        return lowBoundary;
    }
@Test
    void getLowBoundary() {
        final Range.RangeBoundary lowBoundary = Range.RangeBoundary.CLOSED;
        final RangeImpl rangeImpl = new RangeImpl(lowBoundary, 10, 15, Range.RangeBoundary.OPEN);
        assertThat(rangeImpl.getLowBoundary()).isEqualTo(lowBoundary);
    }