@EnabledOnJre for JRE-specific tests in JUnit - Build an Automation Script

Verify method behavior only on Java 17 runtime

Preconditions (2)

Step 1: Create a test method annotated with @EnabledOnJre(JRE.JAVA_17)

Step 2: Inside the test method, call the method that behaves differently on Java 17

Step 3: Assert the expected output or behavior specific to Java 17

✅ Expected Result: The test runs and passes only if the runtime is Java 17; otherwise, it is skipped.

Automation Requirements - JUnit 5

Assertions Needed:

Assert that the method returns the expected value on Java 17

Best Practices:

Use @EnabledOnJre annotation to restrict test execution to specific JRE versions

Use assertions from org.junit.jupiter.api.Assertions

Keep test methods small and focused

Avoid hardcoding JRE version checks inside test logic

Automated Solution

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.condition.EnabledOnJre;
import org.junit.jupiter.api.condition.JRE;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class JreSpecificTest {

    // Method that behaves differently on Java 17
    public String getFeatureMessage() {
        // Simulate behavior
        return "Feature available on Java 17";
    }

    @Test
    @EnabledOnJre(JRE.JAVA_17)
    void testFeatureMessageOnJava17() {
        String message = getFeatureMessage();
        assertEquals("Feature available on Java 17", message, "Message should match on Java 17");
    }
}

This test class uses @EnabledOnJre(JRE.JAVA_17) to run the test only when the runtime is Java 17. The getFeatureMessage() method simulates a feature that is specific to Java 17. The test asserts that the returned message matches the expected string. If the test runs on any other JRE version, it will be skipped automatically by JUnit 5.

This approach keeps the test clean and focused on the Java 17 environment without manual version checks inside the test code.

Common Mistakes - 3 Pitfalls

{'mistake': 'Not using @EnabledOnJre and instead checking System.getProperty("java.version") inside the test', 'why_bad': 'This mixes test logic with environment checks and makes tests harder to read and maintain.', 'correct_approach': 'Use @EnabledOnJre annotation to let JUnit handle version-based test execution cleanly.'}

Using @EnabledOnJre but specifying an unsupported or misspelled JRE version

Writing large tests that combine multiple JRE-specific behaviors in one method

Bonus Challenge

Now add tests for Java 11 and Java 17 using @EnabledOnJre with different expected messages

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