Test-driven development using the JUnit unit testing framework

Test-driven development (TDD) is writing test cases before writing code to ensure that the code conforms to specifications. JUnit is a popular unit testing framework in Java that provides assertion verification test conditions. The TDD process includes: setting up the TDD environment, adding JUnit dependencies and creating an empty test class. Write test cases and follow the steps of schedule, run, assert. Write code to pass tests, focus on making the tests pass rather than making the code perfect.

Using JUnit unit testing framework for test-driven development

What is test-driven development (TDD)

Test-driven development (TDD) is a software development approach in which test cases are written before the actual code is written. This helps ensure that the code adheres to its specifications and reduces the risk of errors.

JUnit Unit Testing Framework

JUnit is a widely used unit testing framework for Java. It provides a rich set of assertions that allow you to easily verify test conditions.

Step 1: Set up the TDD environment

1. Add JUnit dependency to your project:

   <dependency>
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
     <version>4.13.1</version>
     <scope>test</scope>
   </dependency>

2. Write an empty test class:

   import org.junit.Test;
   
   public class MyClassTest {
     @Test
     public void emptyTest() {
     }
   }

Step 2: Write test cases

For each method to be tested, Please write a test case. Test cases should follow the following steps:

1. Arrange (Arrange): Set the required input conditions.
2. Run (Act): Call the method and record the results.
3. Assertion (Assert): Use assertions to verify whether the expected results are consistent with the actual results.

Step Three: Write the Code to Pass the Test

Now that you have your test case, you can start writing the code to make it pass the test. Focus on making the tests pass, not making the code perfect.

Practical case: Calculating factorial

Let us consider the method of calculating factorial:

class Factorial {
  public static int compute(int n) {
    int result = 1;
    for (int i = 2; i <= n; i++) {
      result *= i;
    }
    return result;
  }
}

Test case:

import org.junit.Test;

public class FactorialTest {
  @Test
  public void testFactorial() {
    int expected = 120;
    int actual = Factorial.compute(5);
    assertEquals(expected, actual);
  }
}

Run the test case. The test fails because the method is not implemented correctly. Based on the test case, it can be found that the method does not handle negative numbers correctly. Add logic to handle negative numbers and run the test case again until the test passes.

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