Example of calling nunit3 from nant and exporting an nunit2 test results file.

NantRunningNUnit3ForJenkins

<target name="test" depends="compile">
  <copy file="src/ApplicationUnitTests/bin/${build.configuration}/App.config" tofile="src/Application.config" />
  <exec program="nunit3-console.exe">
    <arg value="src/Application.nunit" />
    <arg value="--config:Release" />
    <arg value="--result=TestResult.xml;format=nunit2" />
  </exec>
  <delete file="src/Application.config" />
</target>