From: Jonathan Kohl <kohljonathan@...>
Date: 2005-03-19T07:14:52+09:00
Subject: Advice on ASCII representation of objects for testing using string compares?

I've written a quick test that checks an input file for an application.
I have a "known good" baseline file, and I want to check the new file
against this. I attempted to serialize each conf file into objects to
do string compares. If the strings are not equal, then we need to check
the file for changes. If they are equal, the input file hasn't changed.

I'm using marshal to serialize each file, but I'm finding that my test
case has some false positives and false negatives using this method. If
I marshal the base line file in one script and store the string in a
file for later use, then with another script read in the configuration
file from the new build and do a comparison, I never get a comparison
of the two strings to be equal. If I do all of the above in one script:
-read in base-line file, marshal to a base-line file
-read in new conf file, marshal to a temp file
-read in both as strings, do a comparison (string1 == string2)
It works most of the time, but sometimes it doesn't work when there is
a change, or when the files are equal. The same thing happens with
checksum.

Any ideas on what might be going on? I'm wondering if with marshal
there are differences in the serialization operation which result in
slightly different strings in some cases.

Is there a better way of reading in these XML conf files and making a
simple ASCII representation for accurate string compares for a fast
failure kind of test? Are there library functions that would do this
reliably?

This is what the code looks like, I could very well be doing something
wrong here:
require 'rexml/document'

#serialize baseline file
xml = REXML::Document.new(File.open("xml/demo.xml"))


File.open("baseline/xml_baseline", "w") do | file |
    Marshal.dump(xml, file)
end

#serialize test file
xml2 = REXML::Document.new(File.open("xml/test_demo.xml"))

File.open("temp", "w") do | file |
    Marshal.dump(xml2, file)
end

line1 = IO.read("baseline/xml_baseline")
puts "line1.id.to_s" + line1.id.to_s

#line1 = file1.readline
puts "xml_baseline is: #{line1.size} characters."
puts "xml_baseline is: #{line1.sum.to_s} checksum."
#file1.close

line2 = IO.read("temp")

#line2 = file2.readline
puts "test_demo is: #{line2.size} characters."
puts "test_demo is: #{line2.sum.to_s} checksum."
#file2.close
puts "line2.id.to_s" + line2.id.to_s


#string compare section
if line1 == line2
   puts "EQUAL!"
else
   puts  "NOT EQUAL! test_demo: " + line2 + "\n"
   puts "xml_baseline: " + line1 + "\n"
end
#end of sting compare section

Thanks;

-Jonathan