Test-driven development (TDD) is a software development approach that emphasizes writing tests before writing the actual code. It helps to improve code quality, maintainability, and enables faster feedback loops. In this blog post, we will explore how to implement TDD with Spring Boot in Java.

Prerequisites

To follow along, you will need the following:

• Java Development Kit (JDK) installed on your machine
• Integrated Development Environment (IDE) such as IntelliJ IDEA or Eclipse
• Spring Boot framework

Step 1: Setup

First, let’s set up a new Spring Boot project. You can either use Spring Initializr (https://start.spring.io/) or create a new project manually. Make sure to include the necessary dependencies, such as Spring Boot Test, JUnit, and Mockito.

Step 2: Write the Test Cases

Once the project is set up, it’s time to write some test cases. In TDD, we start by writing the test cases that assert the expected behavior of our code. Let’s assume we are building a simple calculator application.

Create a new Java class called CalculatorServiceTest and annotate it with @RunWith(SpringRunner.class) and @SpringBootTest. This enables Spring Boot test support for our test class.

@RunWith(SpringRunner.class)
@SpringBootTest
public class CalculatorServiceTest {

    @Test
    public void testAddition() {
        CalculatorService calculatorService = new CalculatorService();
        int result = calculatorService.add(2, 3);
        assertEquals(5, result);
    }

    @Test
    public void testSubtraction() {
        CalculatorService calculatorService = new CalculatorService();
        int result = calculatorService.subtract(5, 2);
        assertEquals(3, result);
    }

    // Add more test cases for multiplication, division, etc.

}

In the above code snippet, we have defined two test cases: testAddition() and testSubtraction(). We create an instance of the CalculatorService class and perform the respective operations, asserting the expected result using JUnit’s assertEquals() method.

Step 3: Implement the Code

Now that we have our test cases, it’s time to implement the code to make them pass. Create a new Java class called CalculatorService and define the methods for addition, subtraction, multiplication, and division.

public class CalculatorService {

    public int add(int a, int b) {
        return a + b;
    }

    public int subtract(int a, int b) {
        return a - b;
    }

    // Add more methods for multiplication, division, etc.
}

Step 4: Run the Tests

To run the tests, simply execute the CalculatorServiceTest class. Depending on your IDE, you can right-click on the class and select “Run Test” or use the JUnit test runner.

If all the tests pass, congratulations! You have successfully implemented TDD with Spring Boot in Java. If any tests fail, go back to Step 3 and fix the code until all the tests pass.

Conclusion

TDD with Spring Boot in Java ensures that your code meets the expected behavior and helps to detect and fix bugs early in the development cycle. By writing tests first, you can have more confidence in your code and make changes with better safety.

#Java #TDD