Building on @garethr's work on nmap-rspec, this adds being able to do multiple hosts, rather than just a single IP/host. Just specify more of those blocks...

gistfile1.txt

[ben@laptop:nmap-rspec2]% rspec -f d -c nmap-rspec.rb
the scan of the IP ranges

Starting Nmap 6.46 ( http://nmap.org ) at 2014-07-06 23:21 EDT
Nmap scan report for 141.101.117.49
Host is up (0.26s latency).
PORT     STATE    SERVICE
20/tcp   filtered ftp-data
21/tcp   filtered ftp
22/tcp   filtered ssh
23/tcp   filtered telnet
25/tcp   filtered smtp
80/tcp   open     http
110/tcp  filtered pop3
443/tcp  filtered https
512/tcp  filtered exec
522/tcp  filtered ulp
1080/tcp filtered socks
8080/tcp open     http-proxy

Nmap done: 1 IP address (1 host up) scanned in 6.49 seconds
  141.101.117.49 does 80/HTTP and, oddly, 8080/SOCKS
  That should be it, any other hosts are bad!

Finished in 6.53 seconds
2 examples, 0 failures

nmap-rspec-fail.rb

#!/usr/bin/env rspec

require 'nmap/program'
require 'nmap/xml'
require 'awesome_print'
require 'resolv'
require 'timeout'

def outdns(ip)
  begin
    Timeout.timeout(1) do
      rdns = Resolv.new.getname ip
      return "/#{rdns}" if rdns
    end
  rescue Timeout::Error, Resolv::ResolvError
  end
end


describe 'the scan of the IP ranges' do

  # I wanted this to work, but it didn't. So can someone teach me about
  # helpers?
  # def helpy(ips, text, ports)
  #   ips.each do |ip|
  #     it "#{ip}#{outdns(ip)} #{text} #{ports.join(' ')}" do
  #       @hosts_ports.should have(ports.size).items
  #       ports.each { |x| @hosts_ports.should include(x) }
  #       @found_ports[ip] = @hosts_ports[ip]
  #     end
  #   end
  # end

  before(:all) do

    file = "nmap-scan-#{Time.new.strftime('%Y%m%d%H%M%S')}.xml"

    unless File.exists? file
      Nmap::Program.scan do |nmap|
        nmap.xml = file
        nmap.targets = '141.101.117.49'
        nmap.ports = [20,21,22,23,25,80,110,443,512,522,8080,1080]
        nmap.aggressive_timing = true   # -T4
        nmap.disable_dns = true         # -n
        #nmap.syn_scan = true            # -sS
      end
    end

    @hosts_ports = {}
    @found_ports = {}
    Nmap::XML.new(file) do |xml|
      xml.each_host do |host|
        host.each_port do |port|
          @hosts_ports[host.ip] ||= []
          @hosts_ports[host.ip] << "#{port.number}/#{port.protocol.to_s}" if port.state == :open
        end
      end
    end
  end

  ## Example:
  #
  # %w[ 1.2.3.4  5.6.7.8 ].each do |ip|
  #   it "#{ip}#{outdns(ip)} should just do thing/proto" do
  #     @hosts_ports[ip].should have(N).items
  #     @hosts_ports[ip].should include('port/proto')
  #     @found_ports[ip] = @hosts_ports[ip]
  #   end
  # end

  %w[ 141.101.117.49 ].each do |ip|
    it "#{ip}#{outdns(ip)} does 80/HTTP, 8080/SOCKS and, oddly, 666/FAIL" do
      @hosts_ports[ip].should include('80/tcp')
      @hosts_ports[ip].should include('8080/tcp')
      @hosts_ports[ip].should include('666/tcp')
      @hosts_ports[ip].should have(3).items
      @found_ports[ip] = @hosts_ports[ip]
    end
  end

  # Now the found ports should be exactly the same as the scanned ports
  # initially. If there's any difference, then we should error.
  it "That should be it, any other hosts are bad!" do
    @hosts_ports.should == @found_ports
  end


  ## Used for testing.
  # it "should output the ports we found" do
  #   ap @hosts_ports
  # end

end

nmap-rspec.rb

#!/usr/bin/env rspec

require 'nmap/program'
require 'nmap/xml'
require 'awesome_print'
require 'resolv'
require 'timeout'

def outdns(ip)
  begin
    Timeout.timeout(1) do
      rdns = Resolv.new.getname ip
      return "/#{rdns}" if rdns
    end
  rescue Timeout::Error, Resolv::ResolvError
  end
end


describe 'the scan of the IP ranges' do

  # I wanted this to work, but it didn't. So can someone teach me about
  # helpers?
  # def helpy(ips, text, ports)
  #   ips.each do |ip|
  #     it "#{ip}#{outdns(ip)} #{text} #{ports.join(' ')}" do
  #       @hosts_ports.should have(ports.size).items
  #       ports.each { |x| @hosts_ports.should include(x) }
  #       @found_ports[ip] = @hosts_ports[ip]
  #     end
  #   end
  # end

  before(:all) do

    file = "nmap-scan-#{Time.new.strftime('%Y%m%d%H%M%S')}.xml"

    unless File.exists? file
      Nmap::Program.scan do |nmap|
        nmap.xml = file
        nmap.targets = '141.101.117.49'
        nmap.ports = [20,21,22,23,25,80,110,443,512,522,8080,1080]
        nmap.aggressive_timing = true   # -T4
        nmap.disable_dns = true         # -n
        #nmap.syn_scan = true            # -sS
      end
    end

    @hosts_ports = {}
    @found_ports = {}
    Nmap::XML.new(file) do |xml|
      xml.each_host do |host|
        host.each_port do |port|
          @hosts_ports[host.ip] ||= []
          @hosts_ports[host.ip] << "#{port.number}/#{port.protocol.to_s}" if port.state == :open
        end
      end
    end
  end

  ## Example:
  #
  # %w[ 1.2.3.4  5.6.7.8 ].each do |ip|
  #   it "#{ip}#{outdns(ip)} should just do thing/proto" do
  #     @hosts_ports[ip].should have(N).items
  #     @hosts_ports[ip].should include('port/proto')
  #     @found_ports[ip] = @hosts_ports[ip]
  #   end
  # end

  %w[ 141.101.117.49 ].each do |ip|
    it "#{ip}#{outdns(ip)} does 80/HTTP and, oddly, 8080/SOCKS" do
      @hosts_ports[ip].should have(2).items
      @hosts_ports[ip].should include('80/tcp')
      @hosts_ports[ip].should include('8080/tcp')
      @found_ports[ip] = @hosts_ports[ip]
    end
  end

  # Now the found ports should be exactly the same as the scanned ports
  # initially. If there's any difference, then we should error.
  it "That should be it, any other hosts are bad!" do
    @hosts_ports.should == @found_ports
  end


  ## Used for testing.
  # it "should output the ports we found" do
  #   ap @hosts_ports
  # end

end

output_of_failure

[ben@laptop:nmap-rspec2]% rspec -f d -c nmap-rspec-fail.rb

the scan of the IP ranges
  141.101.117.49 does 80/HTTP, 8080/SOCKS and, oddly, 666/FAIL (FAILED - 1)
  That should be it, any other hosts are bad! (FAILED - 2)

Failures:

  1) the scan of the IP ranges 141.101.117.49 does 80/HTTP, 8080/SOCKS and, oddly, 666/FAIL
     Failure/Error: @hosts_ports[ip].should include('666/tcp')
       expected ["80/tcp", "8080/tcp"] to include "666/tcp"
     # ./nmap-rspec-fail.rb:76:in `block (3 levels) in <top (required)>'

  2) the scan of the IP ranges That should be it, any other hosts are bad!
     Failure/Error: @hosts_ports.should == @found_ports
       expected: {}
            got: {"141.101.117.49"=>["80/tcp", "8080/tcp"]} (using ==)
       Diff:
       @@ -1 +1,2 @@
       +"141.101.117.49" => ["80/tcp", "8080/tcp"]

     # ./nmap-rspec-fail.rb:85:in `block (2 levels) in <top (required)>'

Finished in 0.00533 seconds
2 examples, 2 failures

Failed examples:

rspec ./nmap-rspec-fail.rb:73 # the scan of the IP ranges 141.101.117.49 does 80/HTTP, 8080/SOCKS and, oddly, 666/FAIL
rspec ./nmap-rspec-fail.rb:84 # the scan of the IP ranges That should be it, any other hosts are bad!