public virtual void test_contains_Currency_same()
        {
            CurrencyPair test = CurrencyPair.of(GBP, GBP);

            assertEquals(test.contains(GBP), true);
            assertEquals(test.contains(USD), false);
            assertEquals(test.contains(EUR), false);
        }
        public virtual void test_contains_Currency_null()
        {
            CurrencyPair test = CurrencyPair.of(GBP, USD);

            assertThrowsIllegalArg(() => test.contains(null));
        }