Instead of hard-coding IDs for `user` and `ruby_gem`, you should use FactoryGirl associations:

```ruby
FactoryGirl.define do
  factory :review do 
    # other attributes
    user
    ruby_gem
  end
end
```
Now, when you create a `review` object using FactoryGirl, it will automatically also create a `user` and `ruby_gem` object for that review.