How to add Scrolling to the HierarchicalDataTemplate items inside TreeView?

Question

I want to add scrollviewer to every child inside TreeView. I can add scrollviewer for TreeView but I cannot apply scrollviewer to children elements. Here is my example of the structure what currently using

<TreeView x:Name="test" ItemsSource="{Binding Root}">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding TestTemplates}"
                                  DataType="{x:Type vm1:TestTemplateViewModel}">
            <Grid>
                <DockPanel>
                    <TextBlock Text="{Binding TextBlock}"/>
                    <Image Source="/Images/Test.png"
                           Visibility="true">
                </DockPanel>
            </Grid>
            <HierarchicalDataTemplate.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Header}"/>
                </DataTemplate>
            </HierarchicalDataTemplate.ItemTemplate>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>