nunit-vs-templates/nunit.tests.sdkstyle.csharp/_preprocess.xml

<?xml version="1.0" encoding="utf-8" ?>
<Preprocess>
    <!--
      You can specify the path where this should show up in the
      Add New Project / Add New Item dialog by setting the value below
      -->
    <TemplateInfo Path="CSharp\Test"/>
    <Replacements Include="*.*" Exclude="*.vstemplate;*.fsproj;*.vbproj;*.jpg;*.png;*.ico;_preprocess.xml;_project.vstemplate.xml">
        <add key="NUnit.Tests" value="$safeprojectname$"/>
    </Replacements>
</Preprocess>