What strategies do you use to write unit tests for your Spring components? Illustrate with a specific example from your experience.

LeetCode #293 - Flip Game Given a string that contains only these two characters: "+" and "-", you need to reverse the signs of the string's segments. A segment is defined as consecutive characters of the same type. You need to generate all possible states after flipping the signs of segments. When you flip a segment, you change the '+'s to '-'s and vice versa. Return the list of all possible states in any order. **Input:** "++--" **Output:** [ "++++", "+--+", "-++-", "-+--", "--++", "----" ] **Constraints:** - The input string will only contain characters '+' and '-'. - The length of the string will be in the range [1, 20].

Can you describe a time when you had to design a backend system to handle a significant scale or load? What architecture did you decide on, and why?