Ruby, windows, command lines and problems

I’ve been building tools for web service testing using Ruby and its SOAP libraries. I hope to write more on this later, but for now, a pointer to a simple problem that took up far too much time.

My test toolkit has three small programs, each providing different services. The first can be passed a list of named test conditions. It queries the database and returns identifiers for data which matches the test condition of interest. This list of identifiers is dumped to a file. The file is passed to the oracle program as input, generating expected results for the items requested. The list of identifiers is also passed to the web service. The output of the oracle and the web service are in the same format, so it’s then a simple case of automatically comparing the two outputs as files, using diff.

I can also use these tools interactively to run ad-hoc queries on the database and web service, so these tools give me a nice interface for exploratory testing, as well as being able to automate and integrate with the build if need be.

The simple batch file to execute all tests looks something like this:

————
‘ 1. Create the list of things to request from the web service
get_test_data_items > datalist.txt

‘ 2. Generate expected results using the list created, and dump the output to a file
generate_expected_results < datalist.txt > expected.txt

‘3. Query web service for the list of items
query_webservice < datalist.txt > actual.txt

‘4. Check that actual matches expected using Unix
diff actual.txt expected.txt
————
Note that the first three commands are ruby scripts, so windows kindly lets me omit the ‘.rb’ extension.

It turns out that this is a bad thing. Letting windows figure out the file association means that the command line fails to send the specified file as standard input to the ruby script.

The telltale error message for this problem is this:

D:/test/query_webservice.rb:32:in `gets’: Bad file descriptor (Errno::EBADF)
from D:/test/query_webservice.rb:32

The simple workaround is to bypass the ruby file association and explicitly invoke ruby:

ruby get_test_data_items.rb > datalist.txt
ruby generate_expected_results.rb < datalist.txt > expected.txt
ruby query_webservice.rb < datalist.txt > actual.txt

Now it all works.

There’s a more detailed description of the problem here: http://mail.python.org/pipermail/python-bugs-list/2004-August/024920.html

As a side note, I’m calling ‘diff’ from the Gnu utilities for Win32 (http://unxutils.sourceforge.net/) package, a collection of unix utilities to make the windows command line a little friendlier. Laziness is what got me into this problem in the first place. In the spirit of laziness, I’ve also installed a bash shell for Windows. By configuring bash to keep a history of the last 5000 commands, I get automatic logging of my test activities as well.