@EnabledOnJre for JRE-specific tests in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable the test only on Java 17.

JUnit

@EnabledOnJre({JRE.[1])
void testFeature() {
    // test code here
}

Drag options to blanks, or click blank then click option'

AJAVA_11

BJAVA_17

CJAVA_8

DJAVA_19

Attempts:

3 left

💡 Hint

Common Mistakes

Using a Java version constant that does not match the intended JRE version.

Forgetting to import the JRE enum.

The @EnabledOnJre annotation uses JRE constants like JAVA_17 to specify the Java version for which the test runs.

2fill in blank

medium

Complete the code to enable the test only on Java 11 and Java 17.

JUnit

@EnabledOnJre({JRE.JAVA_11, JRE.[1])
void testMultipleVersions() {
    // test code here
}

Drag options to blanks, or click blank then click option'

AJAVA_8

BJAVA_19

CJAVA_15

DJAVA_17

Attempts:

3 left

💡 Hint

Common Mistakes

Using a version not supported or not intended for the test.

Syntax errors in the array of JRE versions.

You can specify multiple JRE versions in the @EnabledOnJre annotation by listing them in the array.

3fill in blank

hard

Fix the error in the annotation to correctly enable the test on Java 8.

JUnit

@EnabledOnJre(JRE.[1])
void testLegacySupport() {
    // test code here
}

Drag options to blanks, or click blank then click option'

AJAVA8

BJAVA-8

CJAVA_8

DJAVA8_

Attempts:

3 left

💡 Hint

Common Mistakes

Using JAVA8 without underscore causes a compile error.

Using hyphens or trailing underscores is invalid.

The correct enum constant for Java 8 is JAVA_8 with an underscore, not JAVA8 or other variants.

4fill in blank

hard

Fill both blanks to enable the test only on Java 15 or Java 19.

JUnit

@EnabledOnJre({JRE.[1], JRE.[2])
void testFutureVersions() {
    // test code here
}

Drag options to blanks, or click blank then click option'

AJAVA_15

BJAVA_11

CJAVA_19

DJAVA_8

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing older versions like Java 8 or 11 when the test targets newer versions.

Syntax errors in the array notation.

The test is enabled on Java 15 and Java 19 by listing both versions in the annotation array.

5fill in blank

hard

Fill all three blanks to enable the test on Java 8, Java 11, and Java 17.

JUnit

@EnabledOnJre({JRE.[1], JRE.[2], JRE.[3])
void testMultipleLTS() {
    // test code here
}

Drag options to blanks, or click blank then click option'

AJAVA_8

BJAVA_11

CJAVA_17

DJAVA_19

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to close the array with a closing brace.

Using incorrect enum constants or missing commas.

The annotation enables the test on three LTS Java versions by listing them all in the array.

Practice

1. What is the main purpose of the @EnabledOnJre annotation in JUnit?

easy

A. To run a test only on specified Java Runtime Environment versions

B. To disable a test permanently

C. To run a test on all Java versions except specified ones

D. To enable tests only on the latest Java version

Solution

1. Step 1: Understand the annotation purpose

   <code>@EnabledOnJre

2. Step 2: Match purpose with options

   To run a test only on specified Java Runtime Environment versions correctly states it runs tests only on specified JRE versions, while others describe different behaviors.

3. Final Answer:

   To run a test only on specified Java Runtime Environment versions -> Option A

4. Quick Check:

   @EnabledOnJre = run test on chosen JRE versions [OK]

Hint: Think: runs tests only on chosen Java versions [OK]

Common Mistakes:

• Confusing @EnabledOnJre with disabling tests
• Assuming it runs tests on all versions except specified
• Thinking it only enables tests on the latest Java version

2. Which of the following is the correct syntax to enable a test only on Java 17 using @EnabledOnJre?

easy

A. @EnabledOnJre(javaVersion = "17")

B. @EnabledOnJre(version = 17)

C. @EnabledOnJre(JRE.JAVA_17)

D. @EnabledOnJre(value = "JAVA_17")

Solution

1. Step 1: Recall correct annotation usage

   The correct syntax uses the enum constant from JRE, like @EnabledOnJre(JRE.JAVA_17).

2. Step 2: Compare options

   Only @EnabledOnJre(JRE.JAVA_17) uses the correct enum constant syntax. Others use invalid or incorrect attribute names or formats.

3. Final Answer:

   @EnabledOnJre(JRE.JAVA_17) -> Option C

4. Quick Check:

   Use enum JRE.JAVA_17 inside @EnabledOnJre [OK]

Hint: Use enum JRE.JAVA_17 inside parentheses [OK]

Common Mistakes:

• Using string values instead of enum constants
• Using incorrect attribute names like version or javaVersion
• Missing the enum prefix JRE.

3. Given the test annotated with @EnabledOnJre({JRE.JAVA_11, JRE.JAVA_17}), what happens when running on Java 15?

medium

A. The test runs normally

B. The test is skipped

C. The test fails with an error

D. The test runs but logs a warning

Solution

1. Step 1: Understand the annotation behavior

   The test runs only on Java 11 or Java 17 as specified.

2. Step 2: Check Java 15 behavior

   Since Java 15 is not in the list, the test is skipped automatically.

3. Final Answer:

   The test is skipped -> Option B

4. Quick Check:

   Test runs only on specified JREs, else skipped [OK]

Hint: Test runs only on listed JREs; others skip [OK]

Common Mistakes:

• Assuming test runs on any Java version
• Expecting test to fail instead of skip
• Thinking test logs a warning when skipped

4. Identify the error in this test annotation: @EnabledOnJre(JRE.JAVA_8, JRE.JAVA_11)

medium

A. JRE.JAVA_8 is not a valid enum constant

B. The annotation cannot be used with more than one JRE

C. The annotation requires a string, not enum constants

D. Multiple JREs must be inside curly braces {}

Solution

1. Step 1: Check annotation syntax for multiple JREs

   When specifying multiple JREs, they must be enclosed in curly braces as an array.

2. Step 2: Analyze given annotation

   The annotation uses parentheses with multiple enum constants without braces, which is invalid syntax.

3. Final Answer:

   Multiple JREs must be inside curly braces {} -> Option D

4. Quick Check:

   Multiple JREs need braces: {@code @EnabledOnJre({JRE.JAVA_8, JRE.JAVA_11})} [OK]

Hint: Use curly braces for multiple JREs inside @EnabledOnJre [OK]

Common Mistakes:

• Omitting curly braces for multiple JREs
• Using strings instead of enum constants
• Thinking multiple JREs are not allowed

5. You want to write a test that runs only on Java 8, 11, and 17, but skips on all other versions. Which is the correct way to annotate the test?

hard

A. @EnabledOnJre({JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17})

B. @EnabledOnJre(JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17)

C. @EnabledOnJre(value = {"JAVA_8", "JAVA_11", "JAVA_17"})

D. @EnabledOnJre(versions = {JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17})

Solution

1. Step 1: Recall correct syntax for multiple JREs

   Multiple JREs must be passed as an array inside curly braces using enum constants.

2. Step 2: Evaluate options

   @EnabledOnJre({JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17}) correctly uses @EnabledOnJre({JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17}). @EnabledOnJre(JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17) misses braces, C uses strings instead of enums, D uses a wrong attribute name.

3. Final Answer:

   @EnabledOnJre({JRE.JAVA_8, JRE.JAVA_11, JRE.JAVA_17}) -> Option A

4. Quick Check:

   Use enum array with braces for multiple JREs [OK]

Hint: Use enum array with braces for multiple JREs [OK]

Common Mistakes:

• Missing curly braces for multiple JREs
• Using strings instead of enum constants
• Using incorrect attribute names like versions or value