Software Disruption Patterns

Space Precondition

These are not really testing patterns but patterns of user or program behavior resulting in abnormalities such as colored screens (blue and grey), crash dumps and other support artefacts including performance alerts and UI problem patterns (page 415).

It is often a case that a process checks for free disk space before proceeding, for example, with updates. This precondition may be violated by a user filling disk after the check but before or during installation. Such was the case with our recent Mac OS X update where we did some copying in the background while the update was downloaded that resulted in insufficient space after reboot, then a grey screen after that and subsequent disk corruption and finally OS reinstallation and loss of several hours better spent with other pattern categories.