Should I accept a so long unpaid writing test (reviewing 1900 words and write 350 words) as a part of the hiring process? How could I find a way to say no without saying no?

Hiring process? Have you been given a solid job offer, and are now being hired? Then yes, you gotta do it if you want the job. The reviewing and writing is going to result in a job, so it’s worth it.

If you don’t yet have a job offer, then this reviewing and writing is still part of the APPLICATION process. You’ll be giving them free work, for a slim chance of anything in return. Tell them sorry, I’m no longer interested in the position, and move on to the next. These days we're all doing hundreds of applications, and really can't be doing this unpaid work hundreds of times.

As a teacher, I’ve been asked to give prospective employers demo lessons and lesson plans. I’ve offered them videos of my previous online classes, and lesson plans I’ve already made, as this didn’t require extra work. But, “produce this lesson plan for us, with these exact parameters”? Uh-uh. That’s going after some free work, that they’re probably getting out of a lot of poor suckers. Screw that.