Test Drupal performances across multiple browsers, scenarios, servers, and collect informations that are very useful to improve user experience. We do automation, functional and php unit tests, write documentation about the requirements, deliverables, planning, making estimates, creating mockups, compare solutions and performance.
If you cannot find a module that does exactly what you need then need to write a custom module. First try to find the same functionality in some existing contributed module. Sometimes it is wise to alter or extend an existing module rather then rewriting the functionality from scratch.