implicit DataTemplates vs. sample data vs. blendability - wpf

Question

I have two simple ViewModels, NodeViewModel and LeafViewModel that can be items in a TreeView. Just like below. Templates are applied implictly because I don't want a custom template selector.
<UserControl x:Class="MyProject.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:ViewModels="clr-namespace:MyProject.ViewModels" mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300" d:DataContext="{d:DesignData /SampleData/NodeViewModelSampleData.xaml}">
<UserControl.Resources>
<HierarchicalDataTemplate DataType="{x:Type ViewModels:NodeViewModel}" ItemsSource={Binding Children}>
<StackPanel Orientation="Horizontal">
<CheckBox Content="{Binding Name}" IsChecked="{Binding Result}"/>
</StackPanel>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type ViewModels:LeafViewModel}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}" />
</StackPanel>
</HierarchicalDataTemplate>
</UserControl.Resources>
<TreeView ItemsSource="{Binding Children}" />
</UserControl>
How can I generate sample data in blend that contains a tree with both NodeViewModels and LeafViewModels and then display it as the data in the treeview while still using implict template selection?

Answer 1

In the absence of using some kind of mocking framework, I've found that the easiest way to do this is to just hack together a class that generates instances of my view models and use it as a data source in Blend.
It occurs to me that it might be even easier to just define the test data in XAML, though this is contingent on the view model classes being designed to allow that (e.g. with parameterless constructors and a ContentProperty attribute, among other things).

Answer 2

I think the answer is simple: You can't.
Blend doesn't really work well with implicit datatemplates and template selectors. This is not only true for sample data but also inplace wysiwyg template editing. So for blendability you should try to avoid implict templates and template selectors whenever you can.