@Disabled for skipping tests in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of @Disabled Annotation in JUnit

What is the primary purpose of the @Disabled annotation in JUnit 5?

A To run a test multiple times automatically

B To mark a test as expected to fail

C To enable parallel execution of tests

D To temporarily skip the execution of a test method or class

💡 Hint

Think about why you might want to prevent a test from running temporarily.

The @Disabled annotation is used to skip a test method or an entire test class temporarily. This is useful when a test is broken or not ready to run but you don't want to delete it.

❓ Predict Output

intermediate

Effect of @Disabled on Test Execution Count

Given the following JUnit 5 test class, how many tests will be executed when running this class?

JUnit

import org.junit.jupiter.api.*;

public class SampleTest {

    @Test
    void testOne() {
        System.out.println("Test One");
    }

    @Disabled
    @Test
    void testTwo() {
        System.out.println("Test Two");
    }

    @Test
    void testThree() {
        System.out.println("Test Three");
    }
}

A 2

B 3

C 1

D 0

💡 Hint

Count only tests that are not disabled.

The test method testTwo is annotated with @Disabled, so it will be skipped. The other two tests will run, so total executed tests are 2.

❓ assertion

advanced

Assertion Behavior in Disabled Tests

Consider a test method annotated with @Disabled that contains failing assertions. What will be the test result when running this test?

A The test will be skipped and no assertion failures reported

B The test will fail due to assertion errors

C The test will pass regardless of assertions

D The test will run but report warnings instead of failures

💡 Hint

Think about whether the test code runs at all when disabled.

When a test is annotated with @Disabled, it is skipped entirely. The test method code, including assertions, is not executed, so no failures or passes are recorded for that test.

🔧 Debug

advanced

Why is a Disabled Test Still Running?

A developer added @Disabled to a test method, but the test still runs during the test suite execution. Which of the following is the most likely cause?

A The test runner does not support <code>@Disabled</code>

B The test method is missing the <code>@Test</code> annotation

C The <code>@Disabled</code> annotation was imported from the wrong package

D The test method is private instead of public

💡 Hint

Check the import statements for annotations.

If @Disabled is imported from a wrong or unrelated package, it will not be recognized by JUnit 5, so the test will run as usual.

❓ framework

expert

Combining @Disabled with Conditional Test Execution

In JUnit 5, if a test method is annotated with both @Disabled and a conditional annotation like @EnabledOnOs(OS.WINDOWS), what will happen when running the tests on a Windows machine?

A JUnit will throw an error due to conflicting annotations

B The test will be skipped because @Disabled takes precedence over conditional annotations

C The test will run because the condition is met, ignoring @Disabled

D The test will run only if both annotations allow it, so it runs on Windows

💡 Hint

Consider the priority of @Disabled in test execution.

The @Disabled annotation always disables the test regardless of other conditional annotations. It has the highest priority and causes the test to be skipped.

Practice

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

easy

A. To run a test multiple times

B. To skip a test without deleting its code

C. To mark a test as passed automatically

D. To make a test run faster

Solution

1. Step 1: Understand the role of @Disabled

   The @Disabled annotation tells JUnit to skip running the test method or class.

2. Step 2: Compare with other options

   It does not mark tests as passed, run them multiple times, or affect speed.

3. Final Answer:

   To skip a test without deleting its code -> Option B

4. Quick Check:

   @Disabled skips tests = C [OK]

Hint: Remember: @Disabled means skip test, not delete it [OK]

Common Mistakes:

• Thinking @Disabled runs tests faster
• Confusing @Disabled with @Test
• Assuming @Disabled marks tests as passed

2. Which of the following is the correct syntax to disable a test method with a reason in JUnit?

easy

A. @Skip("Not ready yet")\npublic void testFeature() {}

B. @Disabled public void testFeature() {"Not ready yet"}

C. @Ignore("Not ready yet")\npublic void testFeature() {}

D. @Disabled("Not ready yet")\npublic void testFeature() {}

Solution

1. Step 1: Identify correct annotation and syntax

   JUnit uses @Disabled with an optional string reason in parentheses and quotes.

2. Step 2: Check each option

   @Disabled("Not ready yet")\npublic void testFeature() {} uses correct annotation and syntax. Options A and C use wrong annotations. @Disabled public void testFeature() {"Not ready yet"} places the reason incorrectly.

3. Final Answer:

   @Disabled("Not ready yet")\npublic void testFeature() {} -> Option D

4. Quick Check:

   @Disabled("reason") syntax = B [OK]

Hint: Use @Disabled("reason") with quotes and parentheses [OK]

Common Mistakes:

• Using @Skip or @Ignore instead of @Disabled
• Placing reason outside parentheses
• Missing quotes around reason

3. Consider the following JUnit test class:

@Disabled("Waiting for bug fix")
public class CalculatorTests {
    @Test
    public void testAdd() { /* test code */ }

    @Test
    public void testSubtract() { /* test code */ }
}

What will happen when this test class runs?

medium

A. Both testAdd and testSubtract will be skipped with reason shown

B. Only testAdd will be skipped, testSubtract will run

C. Both tests will run normally

D. Tests will fail due to syntax error

Solution

1. Step 1: Understand class-level @Disabled effect

   When @Disabled is on a class, all tests inside are skipped.

2. Step 2: Check test methods behavior

   Both testAdd and testSubtract will be skipped, and the reason "Waiting for bug fix" will be shown in reports.

3. Final Answer:

   Both testAdd and testSubtract will be skipped with reason shown -> Option A

4. Quick Check:

   Class-level @Disabled skips all tests = D [OK]

Hint: Class @Disabled skips all tests inside it [OK]

Common Mistakes:

• Thinking only first test is skipped
• Assuming tests run despite class @Disabled
• Confusing @Disabled with @Test

4. You wrote this test method:

@Disabled("Feature incomplete")
public void testFeature() {
    assertEquals(5, 2 + 3);
}

But when you run tests, this method still runs. What is the likely problem?

medium

A. The method is missing the @Test annotation

B. The @Disabled annotation is misspelled

C. The test method is private instead of public

D. JUnit does not support @Disabled on methods

Solution

1. Step 1: Check required annotations for test methods

   JUnit requires @Test annotation to recognize a method as a test.

2. Step 2: Analyze given code

   The method has @Disabled but lacks @Test, so JUnit ignores it as a test and does not skip it.

3. Final Answer:

   The method is missing the @Test annotation -> Option A

4. Quick Check:

   Missing @Test means method not recognized as test [OK]

Hint: Always add @Test to test methods even if @Disabled is present [OK]

Common Mistakes:

• Assuming @Disabled alone makes method a test
• Ignoring method visibility rules
• Thinking JUnit does not support @Disabled on methods

5. You want to temporarily disable some tests in a large test suite but still see the reason for skipping in reports. Which approach is best?

hard

A. Remove the @Test annotation from tests to skip

B. Comment out the test methods in the code

C. Add @Disabled("Reason") to each test method you want to skip

D. Use @Disabled on the whole test class without reasons

Solution

1. Step 1: Understand how to skip tests with reasons

   Using @Disabled("Reason") on test methods skips them and shows the reason in reports.

2. Step 2: Compare other options

   Commenting out or removing @Test hides tests but does not show skip reasons. Disabling whole class skips all tests without selective reasons.

3. Final Answer:

   Add @Disabled("Reason") to each test method you want to skip -> Option C

4. Quick Check:

   @Disabled with reason per method shows skip reason [OK]

Hint: Use @Disabled("reason") on methods to skip with explanation [OK]

Common Mistakes:

• Commenting out tests instead of disabling
• Removing @Test hides tests silently
• Disabling whole class loses selective control