Do I need to leave testing entirely to grow?
No. SDET is a testing role with an engineering bar, and it usually pays and scales better than moving sideways into development with no backend history. The constraint is that panels want code you wrote and a suite you were accountable for. Once those exist, your domain and product knowledge stop being a liability and start being the reason you are hired over a fresh developer.
How much coding is actually asked in an SDET interview?
Enough that you cannot fake it, less than a backend loop. Expect one round of language fundamentals and problem solving, one round on framework design, and one on API or debugging scenarios. The design round is where most manual testers lose the offer, because they can describe tools but not explain why the framework was structured that way or what they would change now.
Is Selenium still worth learning, or should I start with Playwright?
Both are hireable and the job market in India still lists Selenium far more often. What matters more is that you can explain waits, locator stability, parallel execution and reporting in whichever one you use, because those concepts transfer. We pick based on what your current employer runs, since a tool you can use at work generates real evidence faster than one you only practise at home.
How long does the transition usually take?
It depends on whether you can build evidence inside your current role. Testers who can volunteer for automation work at their existing company move faster than those preparing entirely outside office hours. Across the 14 verified switches we have full data for, the median time from first session to signed offer was 11 weeks, with a median of 4 offers in hand. That sample is small and covers several different transitions.