```ruby
Given /^an (.+) exists with an? "([^"]*)" of "([^"]*)"$/ do |model, field, value|
  Factory model, field => value
end```

Change mongoid step_definition to match thoughtbot version
user
```ruby
Given /^an (.+) exists with an? (.+) of "([^"]*)"$/ do |model, field, value|
  Factory model, field => value
end```
assistant