Test suites with @Suite in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of JUnit test suite execution

Given the following JUnit 5 test suite setup, what will be the output when running the suite?

JUnit

import org.junit.jupiter.api.Test;
import org.junit.platform.suite.api.SelectClasses;
import org.junit.platform.suite.api.Suite;

@Suite
@SelectClasses({TestA.class, TestB.class})
public class MyTestSuite {}

class TestA {
    @Test
    void testA1() {
        System.out.println("TestA1 executed");
    }
}

class TestB {
    @Test
    void testB1() {
        System.out.println("TestB1 executed");
    }
}

A TestB1 executed\nTestA1 executed

B TestA1 executed\nTestB1 executed

C No output, tests are not executed by @Suite

D Compilation error due to missing @Test annotations

💡 Hint

Remember that @Suite runs all tests in the selected classes in the order they are declared.

The @Suite annotation with @SelectClasses runs all tests in the specified classes. TestA's test runs first, printing 'TestA1 executed', then TestB's test runs, printing 'TestB1 executed'.

❓ assertion

intermediate

Correct assertion to verify test suite execution count

You have a JUnit 5 test suite with two test classes, each containing two tests. Which assertion correctly verifies that the suite ran exactly 4 tests?

JUnit

import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.platform.launcher.Launcher;
import org.junit.platform.launcher.LauncherDiscoveryRequest;
import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
import org.junit.platform.launcher.core.LauncherFactory;
import org.junit.platform.engine.discovery.DiscoverySelectors;
import org.junit.platform.launcher.TestExecutionSummary;
import org.junit.platform.launcher.listeners.SummaryGeneratingListener;

LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
    .selectors(DiscoverySelectors.selectClass(MyTestSuite.class))
    .build();
Launcher launcher = LauncherFactory.create();
SummaryGeneratingListener listener = new SummaryGeneratingListener();
launcher.execute(request, listener);
TestExecutionSummary summary = listener.getSummary();

// Which assertion is correct here?

A assertEquals(4, summary.getTestsFailedCount());

B assertEquals(2, summary.getTestsSucceededCount());

C assertEquals(4, summary.getTestsSucceededCount());

D assertEquals(0, summary.getTestsStartedCount());

💡 Hint

Count all successful tests run by the suite.

Since the suite contains 2 classes with 2 tests each, total tests run and succeeded should be 4. The assertion verifying testsSucceededCount equals 4 is correct.

🔧 Debug

advanced

Identify the cause of suite not running tests

Given this JUnit 5 test suite, why does running MyTestSuite not execute any tests?

JUnit

import org.junit.platform.suite.api.SelectClasses;
import org.junit.platform.suite.api.Suite;
import org.junit.jupiter.api.Test;

@Suite
@SelectClasses({TestX.class})
public class MyTestSuite {}

class TestX {
    void testX1() {
        System.out.println("TestX1 executed");
    }
}

A TestX's test method is missing the @Test annotation.

B The @SelectClasses annotation must include the suite class itself.

C TestX class must be public for tests to run.

D The @Suite annotation is missing @RunWith annotation.

💡 Hint

JUnit 5 requires test methods to be annotated with @Test to be recognized.

The test method testX1 lacks the @Test annotation, so JUnit does not recognize it as a test and does not run it.

❓ framework

advanced

Understanding @Suite and test discovery in JUnit 5

Which statement about JUnit 5's @Suite and test discovery is TRUE?

A @Suite requires specifying test classes explicitly with @SelectClasses or @SelectPackages.

B @Suite automatically discovers all test classes in the project without configuration.

C @Suite can only run tests annotated with @BeforeEach and @AfterEach.

D @Suite replaces the need for @Test annotations inside test classes.

💡 Hint

Think about how JUnit 5 knows which tests to run in a suite.

JUnit 5's @Suite requires explicit selection of test classes or packages using annotations like @SelectClasses or @SelectPackages. It does not auto-discover all tests.

🧠 Conceptual

expert

Best practice for organizing large test suites with @Suite

You have a large project with hundreds of test classes. What is the best practice to organize test suites using @Suite to keep tests maintainable and efficient?

A Use @Suite only for integration tests and run unit tests separately without suites.

B Put all test classes in one huge suite annotated with @SelectClasses listing every test class.

C Avoid using @Suite and run tests individually to reduce complexity.

D Create multiple smaller suites grouping related tests by feature or module, then create a master suite to run all.

💡 Hint

Think about scalability and ease of maintenance.

Organizing tests into smaller suites by feature or module improves maintainability and allows selective test runs. A master suite can aggregate these smaller suites for full runs.