public void Ancestors_Works()
        {
            var parent1 = new Strong().AppendTextContent("leaf node text");

            parent1.Content.Should().HaveCount(1);

            var leafText = parent1.Content.First();

            leafText.Should().NotBeNull();
            leafText.Should().BeOfType <TextItem>();
            (leafText as TextItem) !.Content.Should().Be("leaf node text");

            parent1.Parent.Should().BeNull();
            parent1.GetAncestors().Should().NotBeNull().And.BeEmpty();
            leafText.Parent.Should().Be(parent1);
            var initialAncestors = leafText.GetAncestors();

            initialAncestors.Should().HaveCount(1);
            initialAncestors.Should().Contain(parent1);

            var parent2          = new Emphasis().AppendContent(parent1);
            var updatedAncestors = leafText.GetAncestors();

            updatedAncestors.Should().HaveCount(2);
            updatedAncestors.Should().Contain(parent1);
            updatedAncestors.Should().Contain(parent2);
        }