Testing a Completed Game
Like any other piece of software, Interactive Fiction requires testing before it is finished enough to share with the world. Inform provides tools for doing a certain amount of automated testing; the wider community of interactive fiction enthusiasts provides beta-testers.
Using the Skein and Testing Tools
The Skein panel of the IDE allows us to create an entire script for playing through a game, and replay that script systematically whenever there are changes to the source text. This helps to guarantee that work on one aspect of the source does not introduce unintended bugs in other areas. Aaron Reed's introductory screencast demonstrates how the skein and transcript work.
Using External Resources
On the Inform extensions page there are several extensions designed to help test a game's thoroughness, for instance by detecting incomplete descriptions and inappropriate responses.
There is no substitute for having live players explore a game or interactive story and offer their own feedback on the experience. The IF Beta Site and game-testing.org both help match games with testers; some authors also seek beta-testing help from the same forums that provide coding assistance.