Quiz

📘 Instructions

This quiz is designed to evaluate understanding of:

Unit testing
JUnit 5
Validation
Logging
Debugging
Backend reliability concepts

The learner is encouraged to:

Attempt all questions honestly
Explain reasoning wherever applicable
Focus on understanding rather than memorization

Section 1 - Basic Concepts

Question 1

What is the primary purpose of unit testing?

Options

A. To deploy applications B. To test small units of code independently C. To replace debugging D. To generate logs automatically

Question 2

Which annotation is used to mark a test method in JUnit 5?

Options

A. @Controller B. @Bean C. @Test D. @Service

Question 3

Which assertion verifies that two values are equal?

Options

A. assertNull() B. assertTrue() C. assertEquals() D. assertThrows()

Question 4

What is the purpose of mocking in unit testing?

Options

A. To deploy applications faster B. To replace dependencies during testing C. To create database tables D. To improve UI rendering

Question 5

Which framework is commonly used for mocking in Java?

Options

A. Hibernate B. Mockito C. Maven D. Lombok

Section 2 - Validation Concepts

Question 6

Which annotation ensures a string is not null and not blank?

Options

A. @NotNull B. @Size C. @NotBlank D. @Min

Question 7

Which annotation validates email format?

Options

A. @Email B. @Pattern C. @Value D. @Validated

Question 8

Why is validation important in backend systems?

Options

A. To reduce application size B. To improve UI color themes C. To ensure invalid data is rejected D. To increase CPU usage

Question 9

Which annotation is commonly used in Spring Boot controllers to trigger validation?

Options

A. @Autowired B. @Valid C. @Transactional D. @Primary

Section 3 - Logging Concepts

Question 10

What is the purpose of logging?

Options

A. To compile applications B. To monitor and troubleshoot applications C. To replace databases D. To reduce memory usage

Question 11

Which log level is generally used for serious failures?

Options

A. TRACE B. DEBUG C. INFO D. ERROR

Question 12

Which of the following is considered a bad logging practice?

Options

A. Logging exceptions B. Using meaningful log messages C. Logging passwords and sensitive data D. Using appropriate log levels

Question 13

Which logging framework abstraction is commonly used in Spring Boot?

Options

A. SLF4J B. JDBC C. JPA D. Servlet API

Section 4 - Debugging Concepts

Question 14

What does a stack trace help identify?

Options

A. Database schema B. Runtime error location C. Network bandwidth D. Docker image size

Question 15

Which debugging action enters inside a method during execution?

Options

A. Step Over B. Resume C. Step Into D. Stop

Question 16

What is a common cause of NullPointerException?

Options

A. Accessing a null object reference B. Missing semicolon C. Incorrect import statement D. Invalid package name

Section 5 - Code Analysis

Question 17

Analyze the following code:

```java id=”9bc31j” public int divide(int a, int b) { return a / b; }

What issue can occur?

### Options

A. Compilation failure
B. Memory leak
C. Division by zero exception
D. Syntax error

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## Question 18

Analyze the following code:

```java id="cr18pz"
String name = null;
System.out.println(name.length());

What will happen?

Options

A. Program executes normally B. NullPointerException occurs C. ArithmeticException occurs D. Compilation error occurs

Question 19

Analyze the following validation:

```java id=”mb5v4s” @NotBlank private String username;

Which value is invalid?

### Options

A. `"Aditya"`
B. `"Java"`
C. `"   "`
D. `"Developer"`

---

## Question 20

Analyze the following logging statement:

```java id="djlwm8"
logger.error("Failed to create user", exception);

What is the purpose of passing the exception object?

Options

A. To restart the application B. To log stack trace information C. To create database backup D. To improve performance

Section 6 - Short Answer Questions

Question 21

Explain the difference between:

Unit testing
Integration testing

Question 22

Why should developers avoid using:

```java id=”mwjlwm” System.out.println()

for production logging?

---

## Question 23

What are the benefits of automated testing?

---

## Question 24

Explain the purpose of:

```java id="tr4jlwm"
assertThrows()

Question 25

Why is centralized exception handling useful?

Section 7 - Practical Thinking Questions

Question 26

Suppose an API accepts employee age.

What validations would you add and why?

Question 27

A production issue occurs but there are no logs.

Why does this make troubleshooting difficult?

Question 28

A unit test passes on your machine but fails on another system.

What could be possible reasons?

Question 29

You receive the following stack trace:

text id="qk8z13" NullPointerException at UserService.java:52

What steps would you take to debug the issue?

Question 30

Why should backend engineers think about edge cases while writing code?

🧠 Bonus Challenge Questions

Question 31

What is the difference between:

@NotNull
@NotBlank
@NotEmpty

Question 32

Why should unit tests be independent from each other?

Question 33

What are the risks of insufficient testing in production systems?

Question 34

What information should good log messages contain?

Question 35

Why is debugging considered an important engineering skill?

📋 Submission Instructions

The learner should submit:

Answers to objective questions
Explanations for descriptive questions
Any code snippets requested
Notes explaining debugging thought process

🏁 Expected Outcome

After completing this quiz, the learner should have improved understanding of:

✅ Unit testing fundamentals ✅ Validation concepts ✅ Logging best practices ✅ Debugging approaches ✅ Backend reliability principles ✅ Engineering mindset development

💡 Mentor Notes

The purpose of this quiz is not only evaluation.

It is intended to:

Encourage critical thinking
Reinforce backend engineering practices
Build debugging confidence
Develop production-quality thinking

Discussion after the quiz is strongly encouraged.