IDE integration (IntelliJ, Eclipse) in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

JUnit Test Execution Result in IntelliJ

Given the following JUnit 5 test class, what will be the test execution result shown in IntelliJ's test runner after running this test?

JUnit

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

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

A Test fails with red cross and message 'expected 5 but was 6'.

B Test passes with green checkmark and message '1 test successful'.

C Test is skipped with yellow icon and message 'Test ignored'.

D Test does not run due to compilation error.

💡 Hint

Think about what the assertion is checking and the actual calculation.

The test adds 2 + 3 which equals 5, matching the expected value in assertEquals. Therefore, the test passes and IntelliJ shows a green checkmark with '1 test successful'.

❓ assertion

intermediate

Correct Assertion for Null Check in Eclipse JUnit

In Eclipse, you want to write a JUnit 5 test to verify that a method returns null. Which assertion is correct to use?

JUnit

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

public class UserServiceTest {
    @Test
    void testGetUserReturnsNull() {
        UserService service = new UserService();
        User user = service.getUser("unknown");
        // Which assertion to use here?
    }
}

A assertNull(user);

B assertEquals(null, user);

C assertTrue(user == null);

D assertNotNull(user);

💡 Hint

JUnit provides a specific assertion method for null checks.

assertNull(user) is the recommended JUnit assertion to check if an object is null. It provides clearer test reports in Eclipse and IntelliJ.

🔧 Debug

advanced

Debugging a Failing JUnit Test in IntelliJ

You run a JUnit test in IntelliJ and it fails with an AssertionError. You want to debug the test to find the problem. Which step is NOT part of the correct debugging process in IntelliJ?

A Use the 'Run' button to execute the test without breakpoints.

B Inspect variable values in the debugger when execution pauses at breakpoints.

C Step through the code line by line using the debugger controls.

D Set a breakpoint inside the test method and run the test in debug mode.

💡 Hint

Debugging requires pausing execution to inspect state.

Using the 'Run' button executes the test normally without pausing, so you cannot inspect variables or step through code. Debug mode with breakpoints is needed.

❓ framework

advanced

Configuring JUnit 5 in Eclipse for Maven Project

You have a Maven project in Eclipse and want to use JUnit 5 for testing. Which configuration step is essential to run JUnit 5 tests successfully in Eclipse?

A No configuration needed; Eclipse runs JUnit 5 tests automatically.

B Only add JUnit 4 dependency since Eclipse supports it by default.

C Manually download JUnit 5 jar and add it to the build path without pom.xml changes.

D Add the JUnit 5 dependency in the pom.xml and update the project.

💡 Hint

Maven manages dependencies via pom.xml.

JUnit 5 requires adding its dependency in pom.xml so Maven downloads it and Eclipse can run the tests. JUnit 4 dependency alone won't run JUnit 5 tests.

🧠 Conceptual

expert

Understanding Test Reports in IntelliJ for Parameterized Tests

You run a parameterized JUnit 5 test in IntelliJ with 3 different input sets. How does IntelliJ display the test results in the test runner panel?

JUnit

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.junit.jupiter.api.Assertions.*;

public class MathTest {
    @ParameterizedTest
    @ValueSource(ints = {1, 2, 3})
    void testIsPositive(int number) {
        assertTrue(number > 0);
    }
}

A Shows one test failing if any input fails, no details on which.

B Shows 3 separate tests with no grouping, all passing.

C Shows one test with 3 sub-tests, each passing individually.

D Shows no test results because parameterized tests are unsupported.

💡 Hint

IntelliJ groups parameterized tests under one test name with sub-tests.

IntelliJ displays parameterized tests as one test with expandable sub-tests for each input, showing pass/fail status individually.