How do you choose what to automate and what not to?

When deciding what to automate and what not to, I consider several key factors:

• Frequency of repetition: tasks that are performed often and in a repetitive manner are better to automate to save time.
• Stability of functionality: if the functionality changes frequently, automation may require constant updates, which reduces its effectiveness.
• Criticality of errors: for important and critical scenarios, automation helps quickly identify regressions.
• Complexity and cost of automation: if automation is too complex or expensive, and the benefit is small, it's better to leave manual testing.
• Feasibility of automation: some tests are difficult or impossible to automate (e.g., UX tests, visual checks).

For example, if there is a set of regression tests that run with each release, they should be automated. Exploratory testing or usability tests are better left manual.

Thus, I choose automation where it provides the maximum benefit at reasonable costs.