```ruby
require 'spec_helper'

describe 'Calculating the ETSource datasets' do
  datasets = Atlas::Dataset.all.select do |dataset|
    dataset.enabled && dataset.enabled[:etengine]
  end

  if ENV['DATASET']
    datasets.select! do |dataset|
      ENV['DATASET'] == dataset.key.to_s
    end
  end

  datasets.each do |dataset|
    it "calculates the #{ dataset.key } dataset" do
      Atlas::Runner.new(dataset).calculate
    end
  end
end # Calculating the ETSource dataset
```

Tag slow specs in RSpec examples
user
```ruby
require 'spec_helper'

describe 'Calculating the ETSource datasets', :slow do
  datasets = Atlas::Dataset.all.select do |dataset|
    dataset.enabled && dataset.enabled[:etengine]
  end

  if ENV['DATASET']
    datasets.select! do |dataset|
      ENV['DATASET'] == dataset.key.to_s
    end
  end

  datasets.each do |dataset|
    it "calculates the #{ dataset.key } dataset" do
      Atlas::Runner.new(dataset).calculate
    end
  end
end # Calculating the ETSource dataset
```
assistant