Test core fucntion of sslip.io

- w-x-y-z.sslip.io resolves to w.x.y.z

spec/check-dns_spec.rb

@@ -4,17 +4,19 @@
 # practice using rspec.
 def get_whois_nameservers(domain)
   whois_output = `whois #{domain}`
+  soa = nil
   whois_lines = whois_output.split(/\n+/)
   nameserver_lines = whois_lines.select { |line| line =~ /^NS/ }
   nameservers = nameserver_lines.map { |line| line.split.last }
+  # whois records don't have trail '.'; NS records do; add trailing '.'
+  nameservers.map { |ns| ns << '.' }
   nameservers
 end
 
-describe 'xip.io-style domain' do
+domain = ENV['DOMAIN'] || 'example.com'
-  domain = ENV['DOMAIN'] || 'example.com'
+whois_nameservers = get_whois_nameservers(domain)
-  whois_nameservers = get_whois_nameservers(domain)
-
 
+describe domain do
   context "when evaluating $DOMAIN (\"#{domain}\") environment variable" do
     let (:domain) { ENV['DOMAIN'] }
     it 'is set' do
@@ -25,8 +27,30 @@ describe 'xip.io-style domain' do
     end
   end
 
+  it "should have at least 2 nameservers" do
+    expect(whois_nameservers.size).to be > 1
+  end
+
   whois_nameservers.each do |whois_nameserver|
-    context "Nameserver #{whois_nameserver}" do
+    it "nameserver #{whois_nameserver}'s NS records match whois's #{whois_nameservers}" do
+      dig_nameservers = `dig +short ns sslip.io @#{whois_nameserver}`.split(/\n+/)
+      expect(dig_nameservers.sort).to eq(whois_nameservers.sort)
+    end
+
+    it "nameserver #{whois_nameserver}'s SOA record match" do
+      dig_soa = `dig +short soa sslip.io @#{whois_nameserver}`
+      soa = soa || dig_soa
+      expect(dig_soa).to eq(soa)
+    end
+
+    a = [ rand(256), rand(256), rand(256), rand(256) ]
+    it "resolves #{a.join(".")}.sslip.io to #{a.join(".")}" do
+      expect(`dig +short #{a.join(".") + "." + domain} @#{whois_nameserver}`.chomp).to  eq(a.join("."))
+    end
+
+    a = [ rand(256), rand(256), rand(256), rand(256) ]
+    it "resolves #{a.join("-")}.sslip.io to #{a.join(".")}" do
+      expect(`dig +short #{a.join("-") + "." + domain} @#{whois_nameserver}`.chomp).to  eq(a.join("."))
     end
   end
 end