Add tests for the validation error type.
user
```ruby
# encoding: utf-8

require 'spec_helper'

describe Github::Error::Validations do
  describe '#message' do
    let(:error) { described_class.new(:username => nil) }

    it 'contains the problem in the message' do
      error.message.should include "Attempted to send request with nil arguments"
    end

    it 'contains the summary in the message' do
      error.message.should include "Each request expects certain number of arguments."
    end

    it 'contains the resolution in the message' do
      error.message.should include "Double check that the provided arguments are set to some value."
    end
  end
end # Github::Error::Validations
```
assistant