Saturday, August 21, 2010

Expect Pexpect: Python module to help you automate interactive tests

Many a times we encounter writing a code that requires user input to proceed. Testing and validating such an application can become tedious and frustating. Python implements an elegant solution to cut down the effort needed to "talk to application".

This is called pexpect module, borrowed from Tcl "expect". Pexpect is a tool for controlling and automoating programs. It simple "fools" the application with an user input. It runs the program and monitors the output. When output matches a given pattern, it respond to application mimicking the human intervention.

Pexpect can be extensively used in testing and automation. I found it particularly useful for interacting with application like ssh, ftp, passwd, telnet etc.

It comes packaged with standard Ubuntu 9.10. The version of Python used by me is:

$python --version
Python 2.6.4rc2

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