public void CallTree_CollapseAll()
{
CallTree tree = CreateCallTree();
tree.CollapseAll();
tree.TopLevelNodes[0].IsExpanded.Should().BeFalse();
tree.TopLevelNodes[0].Children[0].IsExpanded.Should().BeFalse();
tree.TopLevelNodes[0].Children[1].IsExpanded.Should().BeFalse();
tree.TopLevelNodes[0].Children[2].IsExpanded.Should().BeFalse();
tree.TopLevelNodes[1].IsExpanded.Should().BeFalse();
tree.TopLevelNodes[2].IsExpanded.Should().BeFalse();
}