JUnit 4 vs JUnit 5 (Jupiter) differences - Automation Approaches Compared

Verify basic test execution and annotation differences between JUnit 4 and JUnit 5

Preconditions (2)

Step 1: Create a test class using JUnit 4 annotations

Step 2: Write a test method annotated with @Test that asserts 2 + 2 equals 4

Step 3: Run the JUnit 4 test and verify it passes

Step 4: Create a test class using JUnit 5 (Jupiter) annotations

Step 5: Write a test method annotated with @Test that asserts 2 + 2 equals 4

Step 6: Run the JUnit 5 test and verify it passes

Step 7: Observe differences in annotations such as @Before vs @BeforeEach and @After vs @AfterEach

Step 8: Observe that JUnit 5 supports @DisplayName for test methods

✅ Expected Result: Both JUnit 4 and JUnit 5 tests run successfully and pass. Differences in annotations and features like @DisplayName are observed.

Automation Requirements - JUnit 5 (Jupiter)

Assertions Needed:

Assert that 2 + 2 equals 4

Verify that @BeforeEach and @AfterEach methods run before and after each test

Verify that @DisplayName annotation sets the test display name

Best Practices:

Use JUnit 5 Jupiter API consistently

Use @BeforeEach and @AfterEach instead of JUnit 4's @Before and @After

Use descriptive @DisplayName for test methods

Keep test methods small and focused

Use assertions from org.junit.jupiter.api.Assertions

Automated Solution

JUnit

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

@DisplayName("JUnit 5 Basic Test Class")
public class JUnit5BasicTest {

    @BeforeEach
    void setup() {
        System.out.println("Setup before each test");
    }

    @AfterEach
    void teardown() {
        System.out.println("Teardown after each test");
    }

    @Test
    @DisplayName("Test addition: 2 + 2 = 4")
    void testAddition() {
        assertEquals(4, 2 + 2, "2 + 2 should equal 4");
    }
}

This test class uses JUnit 5 (Jupiter) annotations.

@BeforeEach runs before each test method to setup test conditions.

@AfterEach runs after each test method to cleanup.

@Test marks the test method.

@DisplayName provides a readable name for the test class and method.

assertEquals verifies the expected result.

This shows the key differences from JUnit 4, which uses @Before, @After, and lacks @DisplayName.

Common Mistakes - 3 Pitfalls

Using JUnit 4 annotations like @Before and @After in JUnit 5 tests

Not importing org.junit.jupiter.api.Assertions and using JUnit 4 assertions

Not using @DisplayName to improve test readability

Bonus Challenge

Now add parameterized tests in JUnit 5 to test addition with multiple input pairs

Show Hint

Practice

1. Which of the following is a key difference between JUnit 4 and JUnit 5 regarding test method visibility?

easy

A. JUnit 4 requires test methods to be public, but JUnit 5 does not.

B. JUnit 5 requires test methods to be public, but JUnit 4 does not.

C. Both JUnit 4 and JUnit 5 require test methods to be private.

D. Neither JUnit 4 nor JUnit 5 require any specific visibility for test methods.

Solution

1. Step 1: Understand JUnit 4 test method visibility

   JUnit 4 requires test methods to be declared as public for the framework to recognize and run them.

2. Step 2: Understand JUnit 5 test method visibility

   JUnit 5 allows test methods to have any visibility, including package-private, making it more flexible.

3. Final Answer:

   JUnit 4 requires test methods to be public, but JUnit 5 does not. -> Option A

4. Quick Check:

   JUnit 4 public test methods = true [OK]

Hint: Remember: JUnit 4 needs public tests; JUnit 5 is more relaxed [OK]

Common Mistakes:

• Thinking JUnit 5 also requires public test methods
• Assuming both versions have the same visibility rules
• Confusing private and public requirements

2. Which annotation replaces @Before from JUnit 4 in JUnit 5?

easy

A. @Init

B. @BeforeAll

C. @Setup

D. @BeforeEach

Solution

1. Step 1: Identify JUnit 4 setup annotation

   JUnit 4 uses @Before to run code before each test method.

2. Step 2: Identify JUnit 5 equivalent annotation

   JUnit 5 replaces @Before with @BeforeEach to clarify it runs before each test method.

3. Final Answer:

   @BeforeEach -> Option D

4. Quick Check:

   @Before in JUnit 4 = @BeforeEach in JUnit 5 [OK]

Hint: Think "Each" means before every test, replacing @Before [OK]

Common Mistakes:

• Choosing @BeforeAll which runs once before all tests
• Using non-existent annotations like @Setup or @Init
• Confusing @BeforeEach with @AfterEach

3. Consider this JUnit 5 test class snippet:

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

class CalculatorTest {
  @Test
  void addTest() {
    int result = 2 + 3;
    assertEquals(5, result);
  }
}

What will be the test result when running this test?

medium

A. Test passes successfully

B. Test fails with assertion error

C. Compilation error due to missing public modifier

D. Runtime error due to missing @BeforeEach

Solution

1. Step 1: Check method visibility in JUnit 5

   The test method is package-private (no modifier), which is allowed in JUnit 5.

2. Step 2: Verify assertion correctness

   The assertion compares 5 and result (2+3=5), so it matches and passes.

3. Final Answer:

   Test passes successfully -> Option A

4. Quick Check:

   2 + 3 = 5, assertion true [OK]

Hint: JUnit 5 allows non-public tests; 2+3=5 means pass [OK]

Common Mistakes:

• Assuming test methods must be public in JUnit 5
• Thinking missing @BeforeEach causes failure here
• Confusing assertion order causing failure

4. Given this JUnit 4 test snippet:

import org.junit.Before;
import org.junit.Test;

public class SampleTest {
  @Before
  public void setup() {
    System.out.println("Setup");
  }

  @Test
  void testMethod() {
    System.out.println("Test");
  }
}

What is the main issue when running this test?

medium

A. No issues; test runs and prints both lines

B. The test method must be public in JUnit 4

C. The setup method must be static

D. The @Before annotation is not recognized in JUnit 4

Solution

1. Step 1: Check test method visibility requirement in JUnit 4

   JUnit 4 requires test methods to be public, but here testMethod() has default (package-private) visibility.

2. Step 2: Verify @Before method correctness

   The setup() method is public and correctly annotated, so no issue there.

3. Final Answer:

   The test method must be public in JUnit 4 -> Option B

4. Quick Check:

   JUnit 4 test methods must be public [OK]

Hint: JUnit 4 needs public test methods; check method modifiers [OK]

Common Mistakes:

• Thinking @Before is invalid in JUnit 4
• Assuming setup must be static
• Believing test runs despite non-public test method

5. You want to migrate a JUnit 4 test class to JUnit 5. Which of these changes is NOT required?

hard

A. Change import statements to JUnit Jupiter packages

B. Replace @Before with @BeforeEach

C. Make all test methods public

D. Replace @Test import to JUnit Jupiter's @Test

Solution

1. Step 1: Identify visibility requirements in JUnit 5

   JUnit 5 does not require test methods to be public; package-private is allowed.

2. Step 2: Check other migration steps

   Replacing @Before with @BeforeEach and updating imports to Jupiter packages are required for migration.

3. Final Answer:

   Make all test methods public -> Option C

4. Quick Check:

   JUnit 5 relaxes method visibility rules [OK]

Hint: JUnit 5 allows non-public tests; no need to change visibility [OK]

Common Mistakes:

• Thinking test methods must be public in JUnit 5
• Forgetting to update import statements
• Missing @Before to @BeforeEach replacement