public void EmpyContainerNode_QueryDescendantNodes_ReturnsNullOrEmpty(Fb2Container node)
{
var firstAllowedChildName = node.AllowedElements.First();
Func <Fb2Node, bool> firstAllowedChildPredicate = nodeToCompare => nodeToCompare.Name.Equals(firstAllowedChildName);
node.GetDescendants(firstAllowedChildName).Should().BeEmpty();
node.GetDescendants(firstAllowedChildPredicate).Should().BeEmpty();
node.GetDescendants <Fb2Node>().Should().BeEmpty();
node.GetDescendants <BodySection>().Should().BeEmpty();
node.GetFirstDescendant(firstAllowedChildName).Should().BeNull();
node.GetFirstDescendant(firstAllowedChildPredicate).Should().BeNull();
node.GetFirstDescendant <Fb2Node>().Should().BeNull();
node.GetFirstDescendant <BodySection>().Should().BeNull();
var success = node.TryGetFirstDescendant(firstAllowedChildName, out var resultNode);
success.Should().BeFalse();
resultNode.Should().BeNull();
var predicateSuccess = node.TryGetFirstDescendant(firstAllowedChildPredicate, out var resultPredicateNode);
predicateSuccess.Should().BeFalse();
resultPredicateNode.Should().BeNull();
var genericSuccess = node.TryGetFirstDescendant <Fb2Node>(out var resultGenericNode);
genericSuccess.Should().BeFalse();
resultGenericNode.Should().BeNull();
var bookBodySuccess = node.TryGetFirstDescendant <BookBody>(out var resultBookBody);
bookBodySuccess.Should().BeFalse();
resultBookBody.Should().BeNull();
}