```ruby
require 'spec_helper'

require 'dm-core'
require 'dm-core/spec/shared/adapter_spec'

require 'dm-migrations'
require 'dm-yaml-adapter/spec/setup'

ENV['ADAPTER']          = 'yaml'
ENV['ADAPTER_SUPPORTS'] = 'all'

describe 'DataMapper::Adapters::YamlAdapter' do

  before :all do
    @adapter    = DataMapper::Spec.adapter
    @repository = DataMapper.repository(@adapter.name)
  end

  it_should_behave_like "An Adapter"

end
```

Add spec for duplicate ids after destroy
user
```ruby
require 'spec_helper'

require 'dm-core'
require 'dm-core/spec/shared/adapter_spec'

require 'dm-migrations'
require 'dm-yaml-adapter/spec/setup'

ENV['ADAPTER']          = 'yaml'
ENV['ADAPTER_SUPPORTS'] = 'all'

describe 'DataMapper::Adapters::YamlAdapter' do

  before :all do
    @adapter    = DataMapper::Spec.adapter
    @repository = DataMapper.repository(@adapter.name)
  end

  it_should_behave_like "An Adapter"

  describe "A YAML database with one record deleted" do

    before :all do
      class ::Example
        include DataMapper::Resource

        property :id,   Serial
        property :name, String
      end

      DataMapper.finalize

      Example.all.destroy
      @obj1 = Example.create :name => "alice"
      @obj2 = Example.create :name => "bob"

      @obj1.destroy
      @obj3 = Example.create :name => "cathy"
    end

    it "should not have duplicate ids" do
      file = @adapter.send(:yaml_file, Example)
      results = YAML.load(open(file).read)
      results[0]["id"].should_not == results[1]["id"]
    end

    it "should find all of the individual records in the db" do
      examples = Example.all

      examples.collect{|e| e.name}.should include "cathy"
      examples.collect{|e| e.name}.should include "bob"
    end
  end
end
```
assistant