SOLID principles in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the Single Responsibility Principle (SRP)

Which of the following best describes the Single Responsibility Principle?

A A class should depend on abstractions, not on concrete implementations.

B A class should have only one reason to change, meaning it should have only one job or responsibility.

C Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness.

D A class should be open for modification but closed for extension.

💡 Hint

Think about how many reasons a class should have to change.

The Single Responsibility Principle states that a class should have only one reason to change, meaning it should focus on a single responsibility or job.

📋 Factual

intermediate

Identifying the Open/Closed Principle (OCP)

Which statement correctly explains the Open/Closed Principle?

A Derived classes must be substitutable for their base classes.

B Classes should have only one responsibility.

C Software entities should be open for extension but closed for modification.

D Depend on concrete classes rather than abstractions.

💡 Hint

Consider how software should behave when new features are added.

The Open/Closed Principle means software components should allow adding new functionality without changing existing code.

🔍 Analysis

advanced

Applying the Liskov Substitution Principle (LSP)

Given a base class Bird with a method fly(), and a subclass Penguin that cannot fly, which problem violates the Liskov Substitution Principle?

A Replacing <code>Bird</code> objects with <code>Penguin</code> objects causes errors when calling <code>fly()</code>.

B Using interfaces to abstract bird behaviors.

C Adding new methods to <code>Bird</code> without changing <code>Penguin</code>.

D Creating a new subclass <code>Eagle</code> that can fly.

💡 Hint

Think about substituting a subclass where the base class is expected.

Liskov Substitution Principle requires that subclasses can replace base classes without breaking the program. If Penguin cannot fly but inherits fly(), substituting it breaks expectations.

❓ Comparison

advanced

Distinguishing Dependency Inversion Principle (DIP)

Which option best illustrates the Dependency Inversion Principle?

A High-level modules depend on abstractions, not on low-level modules.

B Classes should have only one reason to change.

C Derived classes must be substitutable for their base classes.

D Software entities should be open for extension but closed for modification.

💡 Hint

Consider the direction of dependencies between high-level and low-level modules.

The Dependency Inversion Principle states that high-level modules should not depend on low-level modules directly; both should depend on abstractions.

❓ Reasoning

expert

Evaluating Interface Segregation Principle (ISP) in Design

A software system has a large interface Printer with methods print(), scan(), and fax(). Some classes only need print(). What problem arises if these classes implement the full interface?

A The system becomes open for extension but closed for modification.

B Classes will have multiple reasons to change, violating the Single Responsibility Principle.

C Subclasses cannot replace base classes without errors.

D Classes are forced to implement methods they do not use, violating the Interface Segregation Principle.

💡 Hint

Think about interfaces and how they should be designed for clients.

The Interface Segregation Principle says clients should not be forced to depend on interfaces they do not use. Large interfaces cause unnecessary implementation burden.