More helpful error message when a jasmine server is already running

contrib/ruby/jasmine_runner.rb

@@ -133,7 +133,12 @@ module Jasmine
         JsAlert.new
       ])
 
-      Thin::Server.start('0.0.0.0', port, app)
+      begin
+        Thin::Server.start('0.0.0.0', port, app)
+      rescue RuntimeError => e
+        raise e unless e.message == 'no acceptor'
+        raise RuntimeError.new("A server is already running on port #{port}")
+      end
     end
   end
 

contrib/ruby/spec/jasmine_runner_spec.rb

@@ -1,12 +1,14 @@
 require 'spec'
 require 'open-uri'
+require 'thin'
+
 require File.dirname(__FILE__) + '/../jasmine_runner'
 
 describe Jasmine::SimpleServer do
   before do
     @port = Jasmine::find_unused_port
   end
-  
+
   after do
     Jasmine::kill_process_group(@jasmine_server_pid) if @jasmine_server_pid
   end
@@ -25,12 +27,30 @@ describe Jasmine::SimpleServer do
     run_html.should =~ /<script src="file2"/
   end
 
+  describe "RuntimeError" do
+
+    it "should throw an Already Running error if there is already a server running" do
+      Thin::Server.should_receive(:start).and_raise(RuntimeError.new('no acceptor'))
+      lambda {
+        Jasmine::SimpleServer.start(@port, ["file1", "file2"], {})
+      }.should raise_error(RuntimeError, "A server is already running on port #{@port}")
+    end
+
+    it "re-raises other RuntimeErrors" do
+      Thin::Server.should_receive(:start).and_raise(RuntimeError.new('some random error'))
+      lambda {
+        Jasmine::SimpleServer.start(@port, ["file1", "file2"], {})
+      }.should raise_error(RuntimeError, "some random error")
+    end
+
+  end
+
   it "should take a proc that returns a list of spec files" do
     spec_fileses = [["file1", "file2"], ["file1", "file2", "file3"]]
     spec_files_proc = lambda do
       spec_fileses.shift
     end
-    
+
     @jasmine_server_pid = fork do
       Process.setpgrp
       Jasmine::SimpleServer.start(@port, spec_files_proc, {})