Berk depedency with kitchen ci

I cannot figure out to make my cookbook run correctly with kitchen ci. This is what I wrote and execute:

kitchen.yml

driver:
  name: docker
  binary: docker
  use_sudo: false

provisioner:
  name: chef_zero
  always_update_cookbooks: true
  chef_repo_path: ../..
  nodes: ../../nodes

platforms:
  - name: ubuntu-16.04
    driver_plugin: docker

suites:
  - name: default
    data_bags_path: "../../data_bags"
    encrypted_data_bag_secret_key_path: "../../data_bags/secrets/bitbucket.json"
    run_list:
            - recipe[redmine_test]

verifier:
  name: inspec

Berksfile in my cookbook folder:

source 'https://supermarket.chef.io'
metadata
cookbook 'nginx', '~> 2.7.6'
cookbook 'logrotate', '~> 1.9.2'

Commands that I run:

$ berks vendor
$ kitchen create && kitchen converge -l debug

This is the error I get:
 ================================================================================
       Recipe Compile Error in /tmp/kitchen/cache/cookbooks/redmine_test/recipes/default.rb
       ================================================================================

       NoMethodError
       -------------
       undefined method `[]' for nil:NilClass

       Cookbook Trace:
       ---------------
         /tmp/kitchen/cache/cookbooks/redmine_test/recipes/default.rb:73:in `block in from_file'
         /tmp/kitchen/cache/cookbooks/redmine_test/recipes/default.rb:70:in `from_file'

       Relevant File Content:
       ----------------------
       /tmp/kitchen/cache/cookbooks/redmine_test/recipes/default.rb:

        66:      action :add
        67:    end
        68:  end
        69:  
        70:  directory "redmine_repos" do
        71:    path lazy { "#{node['etc']['passwd'][node['redmine']['user']]['dir']}/repos" }
        72:    owner node['redmine']['user']
        73>>   group node['nginx']['group']
        74:    mode 02775
        75:  end
        76:  

How come do I get this error? whereas the group node['nginx']['group'] variable is well defined in the nginx cookbook that has been vendored.

Thanks

nginx cookbook has to be part (depends nginx) of your metadata.rb. Or it has to be on your run_list.

Also, 2.7.6 is pretty old, there is 7.x already.