Structuring unit tests
There are a few major differences between what I understand from your code and what I understand from the post you mention.

Inheritance vs Nesting
Your code suggests that there is a subclass for each tested method, although the post talks about nested classes:


  The structure has a test class per class being tested. That’s not so
  unusual. But what was unusual to me was that he had a nested class for
  each method being tested.


Class per test vs Class per Method
Also, your code example implies that each class contains a single test, which loses all meaning for the class. The post talks about a class per method tested, which mean that it may contain more than one test, but all tests are relevant to the same method.


using Xunit;

public class TitleizerFacts
{
    public class TheTitleizerMethod
    {
        [Fact]
        public void ReturnsDefaultTitleForNullName()
        {
            // Test code
        }

        [Fact]
        public void AppendsTitleToName()
        {
            // Test code
        }
    }



This kind of structure is very similar to how an RSpec test would be structured, having multiple layers of describe blocks for different scopes - class, method, feature...

describe HomeController do

  let (:fixture) { double('fixture') }

  before(:each) do
    # something before each test
  end

  describe '#get_home' do

    before(:each) do
      expect(repository).to receive(:get_id).with(1).and_return(entity)
    end

    let(:result) { subject.GetOne(1) }

    it 'returns result' do
       expect(result).to_not be_nil
    end 

    it 'returns entity data from database' do
       expect(result.content).to eq entity
     end
  end
end