SOLID violations and fixes in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identifying Single Responsibility Principle Violation

Which of the following class designs violates the Single Responsibility Principle (SRP)?

A A class that handles both user authentication and logging user activities.

B A class that only manages user profile data.

C A class dedicated solely to sending email notifications.

D A class that only formats data for display.

💡 Hint

SRP means a class should have only one reason to change.

Option A mixes authentication and logging, which are two different responsibilities. This violates SRP.

❓ Architecture

intermediate

Fixing Open/Closed Principle Violation

You have a payment processing system that requires modifying existing classes to add new payment methods. Which design change best fixes this Open/Closed Principle (OCP) violation?

A Use global variables to switch payment methods inside the existing class.

B Add new methods directly to the existing payment processing class.

C Create a PaymentMethod interface and implement new payment methods as separate classes.

D Duplicate the payment processing class for each new payment method.

💡 Hint

OCP means software entities should be open for extension but closed for modification.

Option C allows adding new payment methods without changing existing code, following OCP.

❓ scaling

advanced

Liskov Substitution Principle Violation Impact

Consider a class hierarchy where a subclass overrides a method but throws exceptions not expected by the base class. What problem does this cause in a large system?

A It breaks Liskov Substitution Principle, causing unexpected runtime errors when using polymorphism.

B It improves performance by handling errors locally.

C It simplifies the base class by moving complexity to subclasses.

D It ensures better encapsulation and hides implementation details.

💡 Hint

Liskov Substitution Principle requires subclasses to be replaceable without altering correctness.

Throwing unexpected exceptions breaks substitutability, causing runtime errors.

❓ tradeoff

advanced

Interface Segregation Principle Tradeoff

Which option best describes a tradeoff when applying Interface Segregation Principle (ISP) strictly in a system with many small interfaces?

A It decreases modularity by merging multiple responsibilities.

B Increased number of interfaces can lead to complexity in managing dependencies.

C It reduces code readability by combining unrelated methods.

D It forces all clients to implement large interfaces even if they use few methods.

💡 Hint

ISP encourages small, client-specific interfaces.

While ISP improves modularity, too many small interfaces can increase dependency management complexity.

❓ estimation

expert

Estimating Impact of Dependency Inversion Principle Violation

A system tightly couples high-level modules directly to low-level modules without abstractions. What is the most significant impact on system maintainability and scalability?

A It allows easier replacement of low-level modules without affecting high-level modules.

B It improves performance by avoiding abstraction overhead.

C It simplifies testing by reducing the number of interfaces.

D Changes in low-level modules require changes in high-level modules, increasing maintenance effort.

💡 Hint

Dependency Inversion Principle promotes depending on abstractions, not concretions.

Tight coupling causes ripple effects of changes, making maintenance and scaling harder.