public void Should_fail_when_urn_not_belong_to_docflow_type_namespace()
            {
                Action action = () => _ = new PfrLetterType("urn:document:fss-sedo-error-exchange-error");

                action.Should().Throw <ArgumentException>();
            }
            public void Should_initialize_with_given_urn()
            {
                var letterType = new PfrLetterType("urn:pfr-letter-category:letter");

                letterType.ToString().Should().Be("urn:pfr-letter-category:letter");
            }
            public void Should_fail_when_given_invalid_urn(string urn)
            {
                Action action = () => _ = new PfrLetterType(urn);

                action.Should().Throw <Exception>();
            }