Unit testing is a very useful method even if you're not trying to follow test-driven development rules. It helps you think about your code as single-purpose isolated components that can be tested independently when you're either developing or refactoring the code.

It's good to keep in mind that unit tests aren't able to catch every bug in the code. Their usefulness depends on scenarios that you can think of, and therefore, you can miss some hardly predictable situations. Unit tests usually don't test the integration of components and the performance of your code. There are also situations that you can't simulate, such as unexpected operation system behavior caused by other processes.

Try to remember that there's a profiler called Observatory right in Dart's VM, and you can easily use it for your needs.