Business Logic and Complexity in Critical Classes

Implications of business logic implementation

We know that the code that implements business logic is among the most complex code in the app. We know that it’s going to have high churn. We know that these two factors mean that business logic code is more likely to have bugs. We also know that bugs in classes widely used throughout the app can cause more serious systemic problems.

So why would we put the code most likely to have bugs in the classes most widely used in the system? Wouldn’t it be extremely wise to keep the complexity and churn on high fan-in classes—which are used in many places—as low as possible?

If the classes most commonly used throughout the system were very stable and not complex, we minimize the chances ...