@MethodSource for factory methods in JUnit - Test Execution Trace

Test Overview

This test uses JUnit's @MethodSource to supply multiple sets of data to a factory method. It verifies that the factory method creates objects correctly for each input.

Test Code - JUnit 5

JUnit

import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;
import java.util.stream.Stream;

class Product {
    private final String name;
    private final int price;

    Product(String name, int price) {
        this.name = name;
        this.price = price;
    }

    String getName() {
        return name;
    }

    int getPrice() {
        return price;
    }
}

public class ProductFactoryTest {

    static Stream<Product> productProvider() {
        return Stream.of(
            new Product("Book", 10),
            new Product("Pen", 2),
            new Product("Notebook", 5)
        );
    }

    @ParameterizedTest
    @MethodSource("productProvider")
    void testProductCreation(Product product) {
        assertNotNull(product);
        assertNotNull(product.getName());
        assertTrue(product.getPrice() > 0);
    }
}

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initializes ProductFactoryTest class	-	PASS
2	JUnit calls productProvider() method to get test data stream	Stream of 3 Product objects is created	-	PASS
3	JUnit runs testProductCreation() with first Product("Book", 10)	Product object with name 'Book' and price 10 is passed to test	assertNotNull(product), assertNotNull(product.getName()), assertTrue(product.getPrice() > 0)	PASS
4	JUnit runs testProductCreation() with second Product("Pen", 2)	Product object with name 'Pen' and price 2 is passed to test	assertNotNull(product), assertNotNull(product.getName()), assertTrue(product.getPrice() > 0)	PASS
5	JUnit runs testProductCreation() with third Product("Notebook", 5)	Product object with name 'Notebook' and price 5 is passed to test	assertNotNull(product), assertNotNull(product.getName()), assertTrue(product.getPrice() > 0)	PASS
6	All parameterized tests complete	All 3 Product objects tested successfully	-	PASS

Failure Scenario

Failing Condition: productProvider() returns a Product with null name or price <= 0

Execution Trace Quiz - 3 Questions

What does the @MethodSource annotation do in this test?

A Runs the test only once

B Supplies multiple Product objects as test inputs

C Creates a mock Product object

D Skips the test if no data is found

Key Result

Using @MethodSource with factory methods allows running the same test logic with different inputs, improving test coverage and reducing code duplication.