//-------------------------------------------------------------------------
        public virtual void test_rateSensitivity()
        {
            ImmutableRatesProvider                    prov      = createProvider(RATE_END);
            ImmutableRatesProvider                    provEndUp = createProvider(RATE_END + EPS_FD);
            ImmutableRatesProvider                    provEndDw = createProvider(RATE_END - EPS_FD);
            InflationEndMonthRateComputation          ro        = InflationEndMonthRateComputation.of(GB_RPIX, START_INDEX_VALUE, REFERENCE_END_MONTH);
            ForwardInflationEndMonthRateComputationFn obsFn     = ForwardInflationEndMonthRateComputationFn.DEFAULT;
            double rateEndUp = obsFn.rate(ro, DUMMY_ACCRUAL_START_DATE, DUMMY_ACCRUAL_END_DATE, provEndUp);
            double rateEndDw = obsFn.rate(ro, DUMMY_ACCRUAL_START_DATE, DUMMY_ACCRUAL_END_DATE, provEndDw);
            PointSensitivityBuilder sensiExpected = InflationRateSensitivity.of(PriceIndexObservation.of(GB_RPIX, REFERENCE_END_MONTH), 0.5 * (rateEndUp - rateEndDw) / EPS_FD);
            PointSensitivityBuilder sensiComputed = obsFn.rateSensitivity(ro, DUMMY_ACCRUAL_START_DATE, DUMMY_ACCRUAL_END_DATE, prov);

            assertTrue(sensiComputed.build().normalized().equalWithTolerance(sensiExpected.build().normalized(), EPS_FD));
        }
        //-------------------------------------------------------------------------
        public virtual void test_rate()
        {
            ImmutableRatesProvider                    prov  = createProvider(RATE_END);
            InflationEndMonthRateComputation          ro    = InflationEndMonthRateComputation.of(GB_RPIX, START_INDEX_VALUE, REFERENCE_END_MONTH);
            ForwardInflationEndMonthRateComputationFn obsFn = ForwardInflationEndMonthRateComputationFn.DEFAULT;
            double rateExpected = RATE_END / START_INDEX_VALUE - 1;

            assertEquals(obsFn.rate(ro, DUMMY_ACCRUAL_START_DATE, DUMMY_ACCRUAL_END_DATE, prov), rateExpected, EPS);
            // explain
            ExplainMapBuilder builder = ExplainMap.builder();

            assertEquals(obsFn.explainRate(ro, DUMMY_ACCRUAL_START_DATE, DUMMY_ACCRUAL_END_DATE, prov, builder), rateExpected, EPS);
            ExplainMap built = builder.build();

            assertEquals(built.get(ExplainKey.OBSERVATIONS).Present, true);
            assertEquals(built.get(ExplainKey.OBSERVATIONS).get().size(), 1);
            ExplainMap explain0 = built.get(ExplainKey.OBSERVATIONS).get().get(0);

            assertEquals(explain0.get(ExplainKey.FIXING_DATE), REFERENCE_END_MONTH.atEndOfMonth());
            assertEquals(explain0.get(ExplainKey.INDEX), GB_RPIX);
            assertEquals(explain0.get(ExplainKey.INDEX_VALUE), RATE_END);
            assertEquals(built.get(ExplainKey.COMBINED_RATE).Value.doubleValue(), rateExpected, EPS);
        }