shared_examples :create_expires do
  at_each_usec do
    it 'creates the given key and expires it' do
      store.create('key','value', expires: min_ttl).should be true
      store['key'].should == 'value'
      advance min_ttl + t_res
      store.key?('key').should be false
    end

    it 'does not change expires if the key exists' do
      store.store('key', 'value', expires: false).should == 'value'
      store.create('key','another value', expires: min_ttl).should be false
      store['key'].should == 'value'
      advance min_ttl + t_res
      store['key'].should == 'value'
      store.key?('key').should be true
    end
  end
end