Java Parameterized test with JUnit: MultiplyTest example

Java Unit Test: Exercise-4 with Solution

Write a Java program that implements parameterized test to verify that a method behaves correctly for different input values.

Sample Solution:

Java Code:

// ParameterizedTest.java

import org.junit.Test;
import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;
import org.junit.runner.RunWith;
import static org.junit.Assert.assertEquals;
import java.util.Arrays;
import java.util.Collection;

public class ParameterizedTest {

    // Example class with the method to be tested
    public static class ExampleClass {
        public int multiply(int a, int b) {
            return a * b;
        }
    }

    // Parameterized test case
    @RunWith(Parameterized.class)
    public static class MultiplyTest {
        private int input1;
        private int input2;
        private int expectedResult;

        // Constructor with parameters
        public MultiplyTest(int input1, int input2, int expectedResult) {
            this.input1 = input1;
            this.input2 = input2;
            this.expectedResult = expectedResult;
        }

        // Parameters for the test cases
        @Parameters
        public static Collection data() {
            return Arrays.asList(new Object[][]{
                    {2, 3, 6},
                    {5, 5, 25},
                    {-1, 4, -4},
                    {0, 8, 0}
            });
        }

        // JUnit test using parameters
        @Test
        public void testMultiply() {
            ExampleClass example = new ExampleClass();
            int result = example.multiply(input1, input2);
            assertEquals(expectedResult, result);
        }
    }

    // Main function to run JUnit tests
    public static void main(String[] args) {
        Result result = JUnitCore.runClasses(MultiplyTest.class);

        // Check if there are any failures
        if (result.getFailureCount() > 0) {
            System.out.println("Test failed:");

            // Print details of failures
            for (Failure failure : result.getFailures()) {
                System.out.println(failure.toString());
            }
        } else {
            System.out.println("All tests passed successfully.");
        }
    }
}

Sample Output:

All tests passed successfully.

Explanation:

The above Java code shows a parameterized JUnit test using the "Parameterized" runner. Here's a brief explanation:

• ExampleClass:
• Defines a simple class named "ExampleClass" with a method "multiply(int a, int b)" that multiplies two integers.
• MultiplyTest:
• A nested static class, "MultiplyTest", is marked with @RunWith(Parameterized.class). It signifies that this class will be run using the "Parameterized" runner.
• Constructor: It has a constructor with parameters (int input1, int input2, int expectedResult) that will be used to pass values for parameterized testing.
• @Parameters method: The "data()" method annotated with @Parameters provides a collection of parameter sets (arrays of inputs and expected results).
• Test Method: The "testMultiply()" method annotated with @Test is the actual JUnit test. It uses the provided parameters to perform the multiplication using the "ExampleClass" and asserts that the result matches the expected value.
• Main Function:
• The "main()" function is used to run the JUnit tests.
• JUnitCore.runClasses(MultiplyTest.class) runs the "MultiplyTest" class using the JUnitCore runner.
• The results are checked, and if there are any test failures, details are printed. Otherwise, a success message is displayed.

Flowchart:

Java Code Editor:

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