[#2330] Uptime should not make redundant system calls

Rewrite of uptime facts and supporting utility methods. Works on unix,
BSD, windows. No longer makes redundant system calls.

Uses Facter::Util::Uptime utility methods:

* Implemented uptime_seconds_unix using /proc/uptime or who -b on unix,
  sysctl on BSD.

  Added unit tests for the behaviors of get_uptime_seconds_unix: read
  from proc/uptime, read uptime from "sysctl -b kern.boottime", read
  uptime from "who -b", and return nil if nothing else works.

* Implemented uptime_seconds_win using the Win32 API.

Facts implemented:

* uptime_{seconds,hours,days}

    Returns the respective integer value.

* uptime

    Returns human readable uptime statistic that preserves original
    behavior.

    Examples:

      3 days
      1 day
      5:08 hours
      0:35 hours

1 files changed, 53 insertions, 0 deletions

diff --git a/spec/unit/util/uptime.rb b/spec/unit/util/uptime.rb
new file mode 100644
index 0000000..9ba6665
--- /dev/null
+++ b/spec/unit/util/uptime.rb
@@ -0,0 +1,53 @@
+#!/usr/bin/env ruby
+
+require File.dirname(__FILE__) + '/../../spec_helper'
+
+require 'facter/util/uptime'
+
+describe Facter::Util::Uptime do
+
+  describe ".get_uptime_seconds_unix" do
+    context "when /proc/uptime is available" do
+      before do
+        uptime_file = File.join(SPECDIR, "fixtures", "uptime", "ubuntu_proc_uptime")
+        Facter::Util::Uptime.stubs(:uptime_file).returns(uptime_file)
+      end
+
+      it "should return the uptime in seconds as an integer" do
+        Facter::Util::Uptime.get_uptime_seconds_unix.should == 5097686
+      end
+
+    end
+
+    it "should use sysctl kern.boottime when /proc/uptime not available" do
+      nonexistent_file = '/non/existent/file'
+      File.exists?(nonexistent_file).should == false
+      Facter::Util::Uptime.stubs(:uptime_file).returns(nonexistent_file)
+      sysctl_output_file = File.join(SPECDIR, 'fixtures', 'uptime', 'sysctl_kern_boottime') # Aug 01 14:13:47 -0700 2010
+      Facter::Util::Uptime.stubs(:uptime_sysctl_cmd).returns("cat #{sysctl_output_file}")
+      Time.stubs(:now).returns Time.parse("Aug 01 15:13:47 -0700 2010") # one hour later
+      Facter::Util::Uptime.get_uptime_seconds_unix.should == 60 * 60
+    end
+
+    it "should use who -b when neither /proc/uptime nor sysctl kern.boottime is available" do
+      nonexistent_file = '/non/existent/file'
+      File.exists?(nonexistent_file).should == false
+      Facter::Util::Uptime.stubs(:uptime_file).returns(nonexistent_file)
+      Facter::Util::Uptime.stubs(:uptime_sysctl_cmd).returns("cat #{nonexistent_file}")
+      who_b_output_file = File.join(SPECDIR, 'fixtures', 'uptime', 'who_b_boottime') # Aug 1 14:13
+      Facter::Util::Uptime.stubs(:uptime_who_cmd).returns("cat #{who_b_output_file}")
+      Time.stubs(:now).returns Time.parse("Aug 01 15:13") # one hour later
+      Facter::Util::Uptime.get_uptime_seconds_unix.should == 60 * 60
+    end
+
+    it "should return nil when none of /proc/uptime, sysctl kern.boottime, or who -b is available" do
+      nonexistent_file = '/non/existent/file'
+      File.exists?(nonexistent_file).should == false
+      Facter::Util::Uptime.stubs(:uptime_file).returns(nonexistent_file)
+      Facter::Util::Uptime.stubs(:uptime_sysctl_cmd).returns("cat #{nonexistent_file}")
+      Facter::Util::Uptime.stubs(:uptime_who_cmd).returns("cat #{nonexistent_file}")
+      Facter::Util::Uptime.get_uptime_seconds_unix.should == nil
+    end
+  end
+
+end