Spring Boot Test-Driven Development (TDD)

Test-Driven Development (TDD) helps you build robust applications by writing tests before implementing business logic. With Spring Boot, writing unit tests is fast, clean, and efficient.

🌟 Why Use TDD in Spring Boot?

• Fail Fast: Catch issues early during development.
• Clean Design: Forces modular, testable code structure.
• Refactor with Confidence: Tests serve as a safety net.
• Documentation: Tests describe intended behavior clearly.

🌟 Prerequisites

Make sure you have:

• ☕ JDK 17+ installed
• 📦 Maven or Gradle
• 🔤 A Java IDE like IntelliJ IDEA or Eclipse

🛠️ Step 1: Add Test Dependencies

Add Spring Boot's test starter to your project.

Maven:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-test</artifactId>
  <scope>test</scope>
</dependency>

Gradle:

testImplementation 'org.springframework.boot:spring-boot-starter-test'

📋 Step 2: Write Your First Test

Create a simple unit test before implementing the service.

• Java
• Kotlin

package com.example.tdd;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class GreetingServiceTest {

    @Test
    void shouldReturnGreetingMessage() {
        GreetingService service = new GreetingService();
        String result = service.greet("World");
        assertEquals("Hello, World!", result);
    }
}

package com.example.tdd

import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Test

class GreetingServiceTest {

    @Test
    fun shouldReturnGreetingMessage() {
        val service = GreetingService()
        val result = service.greet("World")
        assertEquals("Hello, World!", result)
    }
}

📖 Step 3: Implement the Service

Now implement the GreetingService to pass the test.

• Java
• Kotlin

package com.example.tdd;

public class GreetingService {
    public String greet(String name) {
        return "Hello, " + name + "!";
    }
}

package com.example.tdd

class GreetingService {
    fun greet(name: String): String {
        return "Hello, $name!"
    }
}

▶️ Running the Tests

Use your build tool to run the tests:

./mvnw test

Or with Gradle:

gradle test

You should see the test pass ✅

🔄 Refactor and Repeat

Now that your test passes, you can safely refactor your code. TDD is a loop:

1. Red – Write a failing test
2. Green – Make it pass
3. Refactor – Improve the code

Spring Boot with TDD leads to better-designed, maintainable, and testable applications. Start small, test often, and enjoy the confidence of clean code!