/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/ is in libnunit-doc 2.5.10.11092+dfsg-3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/AssemblyInfo.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/ReadMe.txt
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/SampleFixtureExtension.build
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/SampleFixtureExtension.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/SampleFixtureExtension.csproj.gz
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/SampleFixtureExtensionAttribute.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/SampleFixtureExtensionBuilder.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/Tests/
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/Tests/AssemblyInfo.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/Tests/SampleFixtureExtensionTests.cs
/usr/share/doc/nunit/examples/Extensibility/Core/SampleFixtureExtension/Tests/SampleFixtureExtensionTests.csproj