@EnabledOnOs for OS-specific tests in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the test execution result of this JUnit 5 code snippet?

Consider the following JUnit 5 test method annotated with @EnabledOnOs for Windows OS. What will be the test execution result if run on a Linux machine?

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.condition.EnabledOnOs;
import org.junit.jupiter.api.condition.OS;

public class OSTest {
    @Test
    @EnabledOnOs(OS.WINDOWS)
    void testOnlyOnWindows() {
        System.out.println("Running Windows-specific test");
    }
}

A Test runs and prints "Running Windows-specific test" on Linux.

B Test fails with an exception on Linux.

C Test is skipped and not executed on Linux.

D Test runs but is ignored on Linux.

💡 Hint

Think about what @EnabledOnOs does when the OS does not match.

The annotation @EnabledOnOs(OS.WINDOWS) causes the test to run only on Windows OS. On Linux, the test is skipped and not executed.

❓ assertion

intermediate

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

You want to write a test that asserts the current OS is Linux before running OS-specific logic. Which assertion is correct?

JUnit

String osName = System.getProperty("os.name").toLowerCase();

A assertTrue(osName.contains("linux"));

B assertEquals(osName, "Linux");

C assertFalse(osName.equalsIgnoreCase("linux"));

D assertNull(osName);

💡 Hint

OS name strings can vary in case and format.

System property "os.name" returns a string like "Linux" or "linux". Using toLowerCase() and contains("linux") is a safe way to check.

🔧 Debug

advanced

Why does this @EnabledOnOs test run on all OS instead of only Mac?

Examine the code below. The test is intended to run only on Mac OS but runs on Windows and Linux too. Identify the cause.

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.condition.EnabledOnOs;
import org.junit.jupiter.api.condition.OS;

public class MacTest {
    @Test
    @EnabledOnOs(os = OS.MAC)
    void testMacOnly() {
        System.out.println("Running Mac test");
    }
}

A The annotation @EnabledOnOs requires a string parameter, not enum.

B The OS enum MAC is deprecated and ignored.

C The test method must be static to run conditionally.

D The attribute name should be 'value' not 'os' in @EnabledOnOs.

💡 Hint

Check the correct attribute name for @EnabledOnOs annotation.

The correct attribute name for specifying OS in @EnabledOnOs is 'value', not 'os'. Using 'os' causes the annotation to ignore the condition and run the test on all OS.

❓ framework

advanced

How to run a test only on Windows and Linux using @EnabledOnOs?

You want a JUnit 5 test to run only on Windows and Linux OS. Which annotation usage is correct?

A @EnabledOnOs(OS.WINDOWS || OS.LINUX)

B @EnabledOnOs({OS.WINDOWS, OS.LINUX})

C @EnabledOnOs(OS.WINDOWS && OS.LINUX)

D @EnabledOnOs(OS.WINDOWS, OS.LINUX)

💡 Hint

Check how to specify multiple OS values in the annotation array.

The @EnabledOnOs annotation accepts an array of OS enums. The correct syntax is @EnabledOnOs({OS.WINDOWS, OS.LINUX}).

🧠 Conceptual

expert

What happens if @EnabledOnOs is used on a test class with multiple test methods?

If a JUnit 5 test class is annotated with @EnabledOnOs(OS.MAC) and contains multiple test methods, what is the behavior when running on Windows?

A All test methods in the class are skipped on Windows.

B Only test methods individually annotated with @EnabledOnOs run on Windows.

C The test class runs but all test methods fail on Windows.

D The test class runs and all test methods run regardless of OS.

💡 Hint

Class-level annotations affect all contained tests.

When @EnabledOnOs is applied at the class level, it controls execution of all test methods inside. If the OS does not match, all tests are skipped.