Question: I just started working as a QA Automation Engineer to a certain company which provides ERP and CRM services. However, I recently discovered that they have no test case documentation for the testing they do, and just report bugs. I am now having a hard time to automate their tests because I have no reference, what do you think I should do?

Answer: 
Mindmap all the high-level features of the application together with business owners. Go over the map with stakeholders (e.g users, developers, managers, and sponsors). Do a risk assessment with some key people, maybe also analyze brittle areas based on defect reports. 

* Write automated happy-path tests for the highest risk features first.
* Create a test-automation debt backlog, prioritize with stakeholders
* In the meantime write automated tests for past critical defects as well.
* Train developers to write automated tests for new features to stop fill the gap of missing tests.
As detailed in

<https://sqa.stackexchange.com/a/38917/8992>

* Learn about the domain
* Capture the existing functionality using a tool such as Cucumber or RSpec to document it
* Make real tests described in English
* Create Smoke, Happy and Sad cases