Sometimes you have to work with a third-party system or interface that is sending your application dirty data, and you need to account for it in your code in creative ways that may not be obvious to someone who is just reading it.<p>For example in our current project w&#x27;ere working on a front-end piece that connects to a CRM application where no rules or constraints have been set up or enforced for a long time. We&#x27;re talking stuff like zip code fields having values like &quot;I don&#x27;t know&quot; or &quot;XXXXX&quot;. So for every function that receives such values from a lookup, we have to clearly document those edge-cases in the comments and explain how the function deals with them.