@DisplayName for readable names in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of the test display name?

Given the following JUnit 5 test code, what will be the display name shown in the test report for the test method?

JUnit

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Assertions;

public class SampleTest {
    @Test
    @DisplayName("Check addition of two numbers")
    void testAdd() {
        int sum = 2 + 3;
        Assertions.assertEquals(5, sum);
    }
}

A Check addition of two numbers

B testAdd

C void testAdd()

D SampleTest.testAdd

💡 Hint

Look at the @DisplayName annotation value.

The @DisplayName annotation sets a custom, readable name for the test method in reports and IDEs. Here, it is "Check addition of two numbers".

❓ assertion

intermediate

Which assertion correctly verifies the display name in a JUnit 5 test?

You want to write a test that checks if the display name of a test method is "Verify user login". Which assertion code snippet correctly verifies this using JUnit 5's TestInfo parameter?

JUnit

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

public class LoginTest {
    @Test
    @DisplayName("Verify user login")
    void loginTest(TestInfo testInfo) {
        // Assertion goes here
    }
}

A assertEquals("Verify user login", testInfo.getDisplayName());

B assertEquals("loginTest", testInfo.getDisplayName());

C assertTrue(testInfo.getDisplayName().contains("login"));

D assertNotNull(testInfo.getDisplayName());

💡 Hint

TestInfo.getDisplayName() returns the display name set by @DisplayName.

The display name set by @DisplayName is "Verify user login", so the assertion must check equality with that exact string.

🔧 Debug

advanced

Why does the @DisplayName annotation not change the test name in the report?

Consider this JUnit 5 test class: import org.junit.jupiter.api.DisplayName; import org.junit.jupiter.api.Test; public class DebugTest { @Test @DisplayName("Test multiplication") public void multiplyTest() { // test code } } The test report still shows the method name "multiplyTest" instead of "Test multiplication". What is the most likely reason?

A The test method is not public.

B The test runner used does not support @DisplayName annotations.

C The @DisplayName annotation is misspelled.

D JUnit 5 requires @DisplayName to be on the class, not the method.

💡 Hint

Check compatibility of test runners with JUnit 5 features.

Some test runners or IDEs may not support JUnit 5's @DisplayName annotation, causing the default method name to show instead.

🧠 Conceptual

advanced

What is the main benefit of using @DisplayName in JUnit 5 tests?

Why should testers use the @DisplayName annotation in their JUnit 5 test methods?

A To mark tests as deprecated and skip them during execution.

B To change the method name at runtime for reflection purposes.

C To automatically generate test data based on the display name.

D To provide a more readable and descriptive name for tests in reports and IDEs.

💡 Hint

Think about how test reports look and how users read test results.

The @DisplayName annotation helps make test reports easier to understand by showing descriptive names instead of method names.

❓ framework

expert

How to dynamically set @DisplayName using a custom TestTemplate in JUnit 5?

You want to create a JUnit 5 test template that runs multiple times with different inputs and sets a dynamic display name for each invocation. Which approach correctly achieves this?

JUnit

import org.junit.jupiter.api.DisplayNameGeneration;
import org.junit.jupiter.api.DisplayNameGenerator;
import org.junit.jupiter.api.TestTemplate;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestTemplateInvocationContext;
import org.junit.jupiter.api.extension.TestTemplateInvocationContextProvider;
import org.junit.jupiter.api.extension.ExtendWith;
import org.junit.jupiter.api.extension.Extension;
import java.util.List;
import java.util.stream.Stream;

public class DynamicDisplayNameTest {

    @TestTemplate
    @ExtendWith(MyInvocationContextProvider.class)
    void dynamicTest(String input) {
        // test code
    }

    static class MyInvocationContextProvider implements TestTemplateInvocationContextProvider {
        @Override
        public boolean supportsTestTemplate(ExtensionContext context) {
            return true;
        }

        @Override
        public Stream<TestTemplateInvocationContext> provideTestTemplateInvocationContexts(ExtensionContext context) {
            return Stream.of(
                invocationContext("Input A"),
                invocationContext("Input B")
            );
        }

        private TestTemplateInvocationContext invocationContext(String name) {
            return new TestTemplateInvocationContext() {
                @Override
                public String getDisplayName(int invocationIndex) {
                    return "Test with " + name;
                }

                @Override
                public List<Object> getAdditionalArguments() {
                    return List.of(name);
                }

                @Override
                public Stream<Extension> getAdditionalExtensions() {
                    return Stream.empty();
                }
            };
        }
    }
}

A Set display name in a @BeforeEach method using TestInfo.

B Use @DisplayName("Test with " + input) directly on the test method.

C Override getDisplayName(int) in TestTemplateInvocationContext to return dynamic names.

D Use @ParameterizedTest with @ValueSource and @DisplayName annotations.

💡 Hint

TestTemplateInvocationContext allows customizing display names per invocation.

Overriding getDisplayName(int) in TestTemplateInvocationContext lets you set dynamic display names for each test invocation in a TestTemplate.