RSpec: Tagging examples and example groups

In RSpec you can tag examples or example groups with any tags you like simply by saying

describe ReportCreator, slow: true do
  # ..
end

describe ReportCreator do
  it 'generates reports', slow: true do
    # ...
  end
end

You can then only run examples with these tags.

rspec --tag slow
rspec -t slow

# Using the parallel_tests gem
rake "parallel:spec[,,--tag slow]"

Or you can run all examples except the ones with a certain tag:

rspec --tag ~slow # note the ~
rspec -t ~slow

# Using the parallel_tests gem
rake "parallel:spec[,,--tag ~slow]"

You can also assign values to tags, and only run or exclude those tags where the values match a given string.

describe ReportCreator do
  it 'generates reports', speed: 'slow' do
    # ...
  end
end

rspec . --tag speed:slow # Only run examples tagged with speed: 'slow'
rspec . --tag ~speed:slow # Run examples except the ones tagged with speed: 'slow'

You can use the tags for hooks and includes, too.

RSpec.configure do |config|
  config.before(:each, slow: true) do
    # Do one thing here
  end
end

RSpec.configure do |config|
  config.include SlowHelpers, type: :slow
end

Note that RSpec will, although it prints your tags inclusion/exclusion config before the suite run, ignore tag config when you pass it a spec file with a line number. That's even when the line number references a describe or context block, where only some examples should be excluded.