Yesterday I was fixing a bug in an inherited Drupal 7 custom module, and I decided that I was going to add some tests to ensure that the bug was fixed and doesn’t get accidentially re-introduced in the future. The test though required me to have a particular content type and fields which are specific to this site, so weren’t present within the standard installation profile used to run tests.
I decided to convert the custom module into a [Feature][0] so that the content type and it’s fields could be added to it, and therefore present on the testing site once the module is installed.