@DisplayName for readable names in JUnit - Test Execution Trace

Test Overview

This test demonstrates how to use @DisplayName in JUnit to give a readable name to a test method. It verifies that the addition of two numbers returns the correct result.

Test Code - JUnit

JUnit

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

public class CalculatorTest {

    @Test
    @DisplayName("Adding two positive numbers should return their sum")
    void testAddition() {
        int a = 5;
        int b = 7;
        int result = a + b;
        assertEquals(12, result, "Sum should be 12");
    }
}

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and identifies test methods with @Test annotation	JUnit test environment initialized, CalculatorTest class loaded	—	PASS
2	Test runner reads @DisplayName annotation for testAddition method	Test method labeled as 'Adding two positive numbers should return their sum' in test report	—	PASS
3	Test runner executes testAddition method	Variables a=5, b=7 initialized; addition performed	assertEquals(12, result) verifies result is 12	PASS
4	Test runner reports test result with readable name from @DisplayName	Test report shows 'Adding two positive numbers should return their sum' as test name with status PASS	—	PASS

Failure Scenario

Failing Condition: The addition result is incorrect (e.g., result is not 12)

Execution Trace Quiz - 3 Questions

What does the @DisplayName annotation do in this test?

A Skips the test during execution

B Provides a readable name for the test method in reports

C Changes the method name in the code

D Runs the test multiple times

Key Result

Using @DisplayName helps make test reports clearer and easier to understand by giving tests descriptive names instead of method names.

Practice

1. What is the main purpose of using @DisplayName in JUnit tests?

easy

A. To skip a test during execution

B. To change the test execution order

C. To give tests clear, readable names for better understanding

D. To add tags for filtering tests

Solution

1. Step 1: Understand the role of @DisplayName

   @DisplayName is used to provide a human-friendly name to a test method instead of the method name.

2. Step 2: Identify the benefit of readable names

   This helps both technical and non-technical people quickly understand what the test checks when reading reports.

3. Final Answer:

   To give tests clear, readable names for better understanding -> Option C

4. Quick Check:

   @DisplayName = readable test names [OK]

Hint: Remember: @DisplayName makes test names easy to read [OK]

Common Mistakes:

• Thinking @DisplayName changes test order
• Confusing @DisplayName with @Tag
• Assuming @DisplayName skips tests

2. Which of the following is the correct syntax to use @DisplayName in a JUnit 5 test method?

easy

A. @DisplayName = "Test addition method"
void testAdd() {}

B. @DisplayName("Test addition method")
void testAdd() {}

C. @DisplayName: "Test addition method"
void testAdd() {}

D. @DisplayName testAdd("Test addition method") {}

Solution

1. Step 1: Recall correct annotation syntax

   Annotations in Java use @AnnotationName("string") before the method signature.

2. Step 2: Match syntax with options

   @DisplayName("Test addition method") void testAdd() {} correctly uses @DisplayName with parentheses and a string argument before the method.

3. Final Answer:

   @DisplayName("Test addition method") void testAdd() {} -> Option B

4. Quick Check:

   @DisplayName("...") syntax is correct [OK]

Hint: Annotations need @ and parentheses with strings [OK]

Common Mistakes:

• Using = or : instead of parentheses
• Placing @DisplayName after method signature
• Omitting quotes around the display name

3. Given the following test code, what will be the display name shown in the test report?

@Test
@DisplayName("Check if number is positive")
void isPositiveTest() {
    assertTrue(5 > 0);
}

medium

A. isPositiveTest

B. assertTrue(5 > 0)

C. void isPositiveTest()

D. Check if number is positive

Solution

1. Step 1: Identify the effect of @DisplayName

   The @DisplayName annotation overrides the default method name shown in reports with the given string.

2. Step 2: Check the string provided

   The string "Check if number is positive" will be shown instead of the method name.

3. Final Answer:

   Check if number is positive -> Option D

4. Quick Check:

   @DisplayName string replaces method name [OK]

Hint: Display name shows the annotation string, not method name [OK]

Common Mistakes:

• Expecting method name instead of display name
• Confusing method signature with display name
• Thinking assertion text appears as name

4. Identify the error in the following JUnit 5 test code using @DisplayName:

@Test
@DisplayName(Test addition)
void testAdd() {
    assertEquals(4, 2 + 2);
}

medium

A. Missing quotes around the display name string

B. Missing @Test annotation

C. assertEquals arguments are reversed

D. Method name should be public

Solution

1. Step 1: Check @DisplayName syntax

   The display name must be a string literal enclosed in double quotes.

2. Step 2: Identify missing quotes

   Here, Test addition is not in quotes, causing a syntax error.

3. Final Answer:

   Missing quotes around the display name string -> Option A

4. Quick Check:

   @DisplayName needs quotes around text [OK]

Hint: Always put display names inside double quotes [OK]

Common Mistakes:

• Omitting quotes around display name
• Confusing @DisplayName with @Test
• Thinking method must be public in JUnit 5

5. You want to write a JUnit 5 test method with a display name that includes quotes, like: Test "add" method works. Which is the correct way to write the @DisplayName annotation?

hard

A. @DisplayName("Test \"add\" method works")

B. @DisplayName('Test "add" method works')

C. @DisplayName("Test 'add' method works")

D. @DisplayName(Test "add" method works)

Solution

1. Step 1: Understand string escaping in Java annotations

   Double quotes inside a Java string must be escaped with a backslash (\") to be valid.

2. Step 2: Check each option for correct escaping

   @DisplayName("Test \"add\" method works") correctly escapes the inner quotes with \". @DisplayName('Test "add" method works') uses single quotes which are invalid for Java strings. @DisplayName("Test 'add' method works") uses single quotes inside double quotes which is valid but changes the quote style. @DisplayName(Test "add" method works) lacks quotes entirely, causing syntax error.

3. Final Answer:

   @DisplayName("Test \"add\" method works") -> Option A

4. Quick Check:

   Escape inner quotes with backslash in Java strings [OK]

Hint: Escape inner double quotes with \" inside @DisplayName [OK]

Common Mistakes:

• Using single quotes for Java strings
• Not escaping inner double quotes
• Omitting quotes around the display name