public void ConstructorTest()
        {
            // Arrange

            // Act
            var sut = new CertificateCollection();

            // Assert
            sut.Should().NotBeNull("Object must be returned.");
            sut.TotalNumberOfCertificates.Should().Be(0);
            sut.TotalNumberOfCommittedCertificates.Should().Be(0);
            sut.TotalRemainingBalance.Should().Be(0);
        }