diff --git a/lib/puppet/util/checksums.rb b/lib/puppet/util/checksums.rb
index 6f6ea59b5..0d45c6d5a 100644
--- a/lib/puppet/util/checksums.rb
+++ b/lib/puppet/util/checksums.rb
@@ -1,37 +1,74 @@
+# A stand-alone module for calculating checksums
+# in a generic way.
 module Puppet::Util::Checksums
+    # Calculate a checksum using Digest::MD5.
     def md5(content)
         require 'digest/md5'
         Digest::MD5.hexdigest(content)
     end
 
+    # Calculate a checksum of the first 500 chars of the content using Digest::MD5.
+    def md5lite(content)
+        md5(content[0..499])
+    end
+
+    # Calculate a checksum of a file's content using Digest::MD5.
     def md5_file(filename)
         require 'digest/md5'
 
-        incr_digest = Digest::MD5.new()
-        File.open(filename, 'r') do |file|
-            file.each_line do |line|
-                incr_digest << line
-            end
-        end
+        digest = Digest::MD5.new()
+        return checksum_file(digest, filename)
+    end
+
+    # Calculate a checksum of the first 500 chars of a file's content using Digest::MD5.
+    def md5lite_file(filename)
+        File.open(filename, "r") { |f| return md5(f.read(500)) }
+    end
 
-        return incr_digest.hexdigest
+    # Return the :mtime timestamp of a file.
+    def mtime_file(filename)
+        File.stat(filename).send(:mtime)
     end
 
+    # Calculate a checksum using Digest::SHA1.
     def sha1(content)
         require 'digest/sha1'
         Digest::SHA1.hexdigest(content)
     end
 
+    # Calculate a checksum of the first 500 chars of the content using Digest::SHA1.
+    def sha1lite(content)
+        sha1(content[0..499])
+    end
+
+    # Calculate a checksum of a file's content using Digest::SHA1.
     def sha1_file(filename)
         require 'digest/sha1'
 
-        incr_digest = Digest::SHA1.new()
+        digest = Digest::SHA1.new()
+        return checksum_file(digest, filename)
+    end
+
+    # Calculate a checksum of the first 500 chars of a file's content using Digest::SHA1.
+    def sha1lite_file(filename)
+        File.open(filename, "r") { |f| return sha1(f.read(500)) }
+    end
+
+    # Return the :ctime of a file.
+    def timestamp_file(filename)
+        File.stat(filename).send(:ctime)
+    end
+
+    private
+
+    # Perform an incremental checksum on a file.
+    def checksum_file(digest, filename)
         File.open(filename, 'r') do |file|
             file.each_line do |line|
-                incr_digest << line
+                digest << line
             end
         end
 
-        return incr_digest.hexdigest
+        return digest.hexdigest
     end
 end
diff --git a/spec/unit/util/checksums.rb b/spec/unit/util/checksums.rb
new file mode 100755
index 000000000..50c213538
--- /dev/null
+++ b/spec/unit/util/checksums.rb
@@ -0,0 +1,105 @@
+#!/usr/bin/env ruby
+#
+#  Created by Luke Kanies on 2007-9-22.
+#  Copyright (c) 2007. All rights reserved.
+
+require File.dirname(__FILE__) + '/../../spec_helper'
+
+require 'puppet/util/checksums'
+
+describe Puppet::Util::Checksums do
+    before do
+        @summer = Object.new
+        @summer.extend(Puppet::Util::Checksums)
+    end
+
+    class LineYielder
+        def initialize(content)
+            @content = content
+        end
+
+        def each_line
+            @content.split("\n").each { |line| yield line }
+        end
+    end
+
+    content_sums = [:md5, :md5lite, :sha1, :sha1lite]
+    file_only = [:timestamp, :mtime]
+
+    content_sums.each do |sumtype|
+        it "should be able to calculate %s sums from strings" % sumtype do
+            @summer.should be_respond_to(sumtype)
+        end
+    end
+
+    [content_sums, file_only].flatten.each do |sumtype|
+        it "should be able to calculate %s sums from files" % sumtype do
+            @summer.should be_respond_to(sumtype.to_s + "_file")
+        end
+    end
+
+    {:md5 => Digest::MD5, :sha1 => Digest::SHA1}.each do |sum, klass|
+        describe("when using %s" % sum) do
+            it "should use #{klass} to calculate string checksums" do
+                klass.expects(:hexdigest).with("mycontent").returns "whatever"
+                @summer.send(sum, "mycontent").should == "whatever"
+            end
+
+            it "should use incremental #{klass} sums to calculate file checksums" do
+                digest = mock 'digest'
+                klass.expects(:new).returns digest
+
+                file = "/path/to/my/file"
+
+                # Mocha doesn't seem to be able to mock multiple yields, yay.
+                fh = LineYielder.new("firstline\nsecondline")
+
+                File.expects(:open).with(file, "r").yields(fh)
+
+                digest.expects(:<<).with "firstline"
+                digest.expects(:<<).with "secondline"
+                digest.expects(:hexdigest).returns :mydigest
+
+                @summer.send(sum.to_s + "_file", file).should == :mydigest
+            end
+        end
+    end
+
+    {:md5lite => Digest::MD5, :sha1lite => Digest::SHA1}.each do |sum, klass|
+        describe("when using %s" % sum) do
+            it "should use #{klass} to calculate string checksums from the first 500 characters of the string" do
+                content = "this is a test" * 100
+                klass.expects(:hexdigest).with(content[0..499]).returns "whatever"
+                @summer.send(sum, content).should == "whatever"
+            end
+
+            it "should use #{klass} to calculate a sum from the first 500 characters in the file" do
+                digest = mock 'digest'
+
+                file = "/path/to/my/file"
+
+                fh = mock 'filehandle'
+                File.expects(:open).with(file, "r").yields(fh)
+
+                fh.expects(:read).with(500).returns('my content')
+
+                klass.expects(:hexdigest).with("my content").returns :mydigest
+
+                @summer.send(sum.to_s + "_file", file).should == :mydigest
+            end
+        end
+    end
+
+    {:timestamp => :ctime, :mtime => :mtime}.each do |sum, method|
+        describe("when using %s" % sum) do
+            it "should use the '#{method}' on the file to determine the timestamp" do
+                file = "/my/file"
+                stat = mock 'stat', method => "mysum"
+
+                File.expects(:stat).with(file).returns(stat)
+
+                @summer.send(sum.to_s + "_file", file).should == "mysum"
+            end
+        end
+    end
+end