StTest/MyTests/MainWindow.xaml

<Window x:Class="MyTests.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:MyTests"
        mc:Ignorable="d"
        Title="MainWindow" 
        Height="450" 
        Width="800">
    <Grid>
        
    </Grid>
</Window>