```ruby
require 'spec_helper'
require 'compo'

describe Compo::HashBranch do
  describe '#initialize' do
    it 'initialises with a Parentless as parent' do
      expect(subject.parent).to be_a(Compo::Parentless)
    end

    it 'initialises with an ID function returning nil' do
      expect(subject.id).to be_nil
    end
  end
end
```

Include hash composite examples in HashBranch.
user
```ruby
require 'spec_helper'
require 'compo'
require 'hash_composite_spec'

describe Compo::HashBranch do
  describe '#initialize' do
    it 'initialises with a Parentless as parent' do
      expect(subject.parent).to be_a(Compo::Parentless)
    end

    it 'initialises with an ID function returning nil' do
      expect(subject.id).to be_nil
    end
  end

  it_behaves_like 'a hash composite'
end
```
assistant