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Introducing TextTest and Acceptance Testing
About Texttest
Background
We feel that the world still produces way too much software that is frankly substandard. The reasons for this are pretty simple: software producers do not pay enough attention to testing, or rely too heavily on manual testing. Manual testing should be focussed on examining the user experience and finding complex bugs, and too often it is used for simple regression testing : to check that the latest release does not crash on startup.
We are warm adherents of Agile Development practices, and practitioners of Extreme Programming. We believe that the Agile movement has improved the software quality situation a great deal, by moving testing to the centre of the development process and making developers directly responsible for verifying the quality of their code. Since 2000 we have been exploring different ways of creating high-level tests that communicate intent and can be understood and created by non-technical customers (Acceptance Tests). The front end and common factor is a tool called TextTest.
Verifying Application Behaviour with TextTest
As the name suggests, TextTest works via comparing plain text logged by programs with a previous 'gold standard' version of that text. This is in contrast to most acceptance testing frameworks on offer today, which generally use some form of hand-written 'assertions' by the test writer that call into an application API.
So, when your test fails and you click on it to see what went wrong, you might see this (Click to Enlarge):
On the left you see what we wanted the program to produce. On the right we see what actually happened. This is testing a small 'video store' application, and this test checks that the same movie cannot be added twice. Given what happened, it obviously can right now...
The focus is around testing a particular executable program with a variety of inputs. To start with, a plain text configuration file is created that tells TextTest about your program, how to run it, and how to test it. Tests (and test suites) are then defined entirely using plain text files in a directory structure.
A test is defined partly by the expected files and their contents that should be produced, and partly by the 'input' to provide, which can consist any or all of:
  • Options to be provided on the command line
  • A file to be redirected to standard input
  • Environment variables that should be set
  • A sequence of 'use-case' actions to be performed on a GUI (see StoryText)
The application needs to write a log file describing what is happening, similar to the one shown above. Any output at all can be compared, so long as it is plain text, or can be converted to it.
For people wanting to test a GUI (custom or Web) you will need some scripting approach to that GUI so that tests can be run without needing somebody to click the buttons. For Python and Java GUIs we have the tool StoryText, which is especially designed to work with TextTest.


Last updated: 04 December 2009