class RSpec::Core::Configuration

def fail_fast=(value)
  case value
  when true, 'true'
    @fail_fast = true
  when false, 'false', 0
    @fail_fast = false
  when nil
    @fail_fast = nil
  else
    @fail_fast = value.to_i
    if value.to_i == 0
      # TODO: in RSpec 4, consider raising an error here.
      RSpec.warning "Cannot set `RSpec.configuration.fail_fast`" \
        " to `#{value.inspect}`. Only `true`, `false`, `nil` and integers" \
        " are valid values."
      @fail_fast = true
    end
  end
end