public void TestTraktShowFilterWithCertifications()
        {
            var filter = new TraktShowFilter();

            filter.WithCertifications(null);
            filter.Certifications.Should().NotBeNull().And.BeEmpty();

            filter.WithCertifications(null, "cert1");
            filter.Certifications.Should().NotBeNull().And.HaveCount(1);

            filter.AddCertifications("cert1", "cert2");
            filter.Certifications.Should().NotBeNull().And.HaveCount(3);

            filter.WithCertifications(null);
            filter.Certifications.Should().NotBeNull().And.BeEmpty();

            filter.WithCertifications(null, "cert1");
            filter.Certifications.Should().NotBeNull().And.HaveCount(1);

            filter.WithCertifications("cert1", "cert2");
            filter.Certifications.Should().NotBeNull().And.HaveCount(2);

            filter.WithCertifications("cert1", "cert2", "cert3", "cert4");
            filter.Certifications.Should().NotBeNull().And.HaveCount(4);

            filter.WithCertifications("cert5");
            filter.Certifications.Should().NotBeNull().And.HaveCount(1);
        }