Friday, November 11, 2005

Automated testing using Ruby

So here’s the problem statement: Write a Ruby script that will open a database, check it for accuracy, and if it is NOT accurate, send an email describing the issues.

So this will require (a) opening a database in Ruby, (b) running a test in Ruby, and (c) sending an email in Ruby. None of these is probably very difficult, but not being a Ruby expert I went searching for examples on the web. I wasn’t thrilled by the examples I found for these tasks, so I thought I’d write up what I did.

Databases: This is code that will open an Access database and grab all of the rows in the Exam table:


require 'dbi'

DBI.connect("DBI:ODBC:driver=Microsoft Access Driver
(*.mdb);dbq=" +
ENV['TESTINSTALLDIR'] + "db1.mdb ") do dbh

rows =
dbh.select_all('select * from Exam')
end

Tests: I started by writing my own little test procedures, until I stepped back and looked at what I’d done – I’d developed a rudimentary RUnit, along the lines of NUnit or CPPUnit. At that point I was sure that it had been done before, and it had – and not only that, but it turned out to be part of the Ruby standard library. Although what I’m doing here isn’t really what I would call unit testing, it’s close enough that I decided to use that instead.


require 'test/unit'
require 'test/unit/ui/console/testrunner'

class
DatabaseTest < Test::Unit::TestCase
def test_dbContents
assert(rows[1]["Media Type"] == "Image Server")
end
end

Test::Unit::UI::Console::TestRunner.run(DatabaseTest)

Email: There are some good email sending examples around. I started with this one and ended here:


require 'net/smtp'

class FailCounter

def TextBody()
email_text = <<END_EMAIL
To: "Ben Fulton"
<#{@to_addr}>
From: #{@from_addr}
Subject: #{@project}
automated test failure

An automated assertion failed for the project
#{@project}

#{@errors}

END_EMAIL

return email_text
end

def Finalize
if (@counter > 0)

Net::SMTP.start("myprovider.net") do smtp
smtp.sendmail( TextBody(),
@from_addr, @to_addr )
end
else
puts "No failures!"
end
end
end

Now, my goal was for the results of the test to be put into the email. That took a long time to figure out. Step 1 of the solution was to realize what the automated test runner was doing under the covers, and take advantage of it. So I replaced the run(DatabaseTest) line with this:


tr = Test::Unit::UI::Console::TestRunner.new( DownloaderTest)
passed = tr.start()
Now I have the results back in a TestResult, which I can examine for failures, so emails only go out if some tests actually failed:


if (passed.failure_count() > 0 passed.error_count() > 0)
fc =
FailCounter.new
fc.Add( “Failures found” )
fc.Finalize()
end

Step 2 of the solution is to get the information from the test in a format that I can put in an email. It turns out that TestRunner.new can take a parameter defining where output should go, which defaults to STDOUT. I could have redirected it to a file, but that seemed like unnecessary work, so after a lot of searching I came up with what I was looking for, StringIO, which takes output and writes it to a string:

sio = StringIO.new
tr = Test::Unit::UI::Console::TestRunner.new(
DownloaderTest, Test::Unit::UI::VERBOSE, sio )

I also changed the default NORMAL verbosity parameter to VERBOSE. Then I replace the FailCounter “Failures found” line like this:

fc.Add( “Failures found: “ + sio.string )

And that was it. I’m not going to glue all this code together here, since this post is already too long, but hopefully if you’re interested it should be straightforward. Good luck!


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