If you are already familiar with OOP and want to quickly get up to speed with the Dart programming language. I recommend heading over to the Dart Track on Exercism and completing the track as well as extra exercises.

or

If you are completely new to programming and want to test yourself as you progress through the course, I recommend starting with the first 3 exercises in the Dart Track on Exercism and progressing as your capability grows. This might mean coming back to Exercism when you learn more Dart concepts through the course.