We could include these messages in the definition of these errors:

```ruby
class InvalidStepError < RuntimeError
  def initialize
    msg = "The requested step did not match any steps defined for this controller."
    super msg
  end
end
```

Then we could make this line:

```ruby
raise UndefinedStepsError.new if steps.nil?
raise InvalidStepError.new if the_step.nil?
```

Which I generally prefer.