Timeout annotations in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a timeout of 100 milliseconds on the test method.

JUnit

@Test
@Timeout([1])
void testQuickOperation() {
    // test code here
}

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

A10

B1000

C100

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1000 instead of 100 causes longer timeout than intended.

Omitting the @Timeout annotation means no timeout is set.

The @Timeout annotation takes the timeout duration in milliseconds. Here, 100 means the test must finish within 100 ms.

2fill in blank

medium

Complete the code to import the Timeout annotation from JUnit Jupiter.

JUnit

import org.junit.jupiter.api.[1];

public class MyTests {
    @Test
    @Timeout(200)
    void testMethod() {}
}

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

ATest

BAfterAll

CBeforeEach

DTimeout

Attempts:

3 left

💡 Hint

Common Mistakes

Importing @Test instead of @Timeout.

Using annotations from other packages.

The Timeout annotation is imported from org.junit.jupiter.api.Timeout to set time limits on tests.

3fill in blank

hard

Fix the error in the timeout annotation usage to specify the time unit as seconds.

JUnit

@Test
@Timeout(value = 2, unit = [1])
void testWithSecondsTimeout() {
    // test code
}

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

AChronoUnit.SECONDS

BTimeUnit.SECONDS

CTimeUnit.MILLISECONDS

DDuration.SECONDS

Attempts:

3 left

💡 Hint

Common Mistakes

Using ChronoUnit which is for date/time, not Timeout.

Using Duration.SECONDS which does not exist.

The Timeout annotation uses java.util.concurrent.TimeUnit to specify the time unit. Use TimeUnit.SECONDS for seconds.

4fill in blank

hard

Fill both blanks to set a timeout of 500 milliseconds using the Timeout annotation with explicit value and unit.

JUnit

@Test
@Timeout(value = [1], unit = [2])
void testHalfSecondTimeout() {
    // test code
}

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

A500

B1000

CTimeUnit.MILLISECONDS

DTimeUnit.SECONDS

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up value and unit parameters.

Using seconds unit with 500 value expecting milliseconds.

Set value to 500 and unit to TimeUnit.MILLISECONDS to specify a 500 ms timeout.

5fill in blank

hard

Fill all three blanks to create a test method with a 3-second timeout and a descriptive display name.

JUnit

@Test
@Timeout(value = [1], unit = [2])
@DisplayName([3])
void testTimeoutWithName() {
    // test code
}

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

A3

BTimeUnit.SECONDS

C"Test with 3 seconds timeout"

D"Timeout test"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect unit for timeout.

Forgetting quotes around display name string.

Set value to 3, unit to TimeUnit.SECONDS, and display name to "Test with 3 seconds timeout" for clarity.

Practice

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

easy

A. To mark a test as expected to fail

B. To repeat a test multiple times automatically

C. To skip a test during execution

D. To stop a test if it runs longer than a specified time limit

Solution

1. Step 1: Understand the role of @Timeout

   The @Timeout annotation sets a maximum time limit for a test method to run.

2. Step 2: Identify what happens when time limit is exceeded

   If the test runs longer than the specified time, it is stopped and marked as failed.

3. Final Answer:

   To stop a test if it runs longer than a specified time limit -> Option D

4. Quick Check:

   @Timeout stops long tests = A [OK]

Hint: Timeout means stop test if too slow [OK]

Common Mistakes:

• Confusing timeout with repeating tests
• Thinking timeout skips tests
• Assuming timeout marks tests as expected failures

2. Which of the following is the correct way to set a timeout of 5 seconds on a JUnit 5 test method?

easy

A. @Timeout(5)

B. @Timeout(5, SECONDS)

C. @Timeout(value = 5, unit = TimeUnit.SECONDS)

D. @Timeout(value = 5, unit = SECONDS)

Solution

1. Step 1: Recall JUnit 5 @Timeout syntax

   The @Timeout annotation requires a value and a time unit specified as an enum from java.util.concurrent.TimeUnit.

2. Step 2: Match correct syntax

   @Timeout(value = 5, unit = TimeUnit.SECONDS) uses named parameters with value=5 and unit=TimeUnit.SECONDS, which is correct syntax.

3. Final Answer:

   @Timeout(value = 5, unit = TimeUnit.SECONDS) -> Option C

4. Quick Check:

   Use named params with TimeUnit enum = C [OK]

Hint: Use named params and TimeUnit enum for timeout [OK]

Common Mistakes:

• Omitting the time unit
• Using wrong enum or missing TimeUnit prefix
• Passing timeout as single unnamed parameter

3. Consider this JUnit 5 test method:

@Test
@Timeout(value = 2, unit = TimeUnit.SECONDS)
void testSleep() throws InterruptedException {
    Thread.sleep(3000);
}

What will happen when this test runs?

medium

A. The test will fail due to timeout after 2 seconds

B. The test will pass after sleeping 3 seconds

C. The test will fail immediately with an exception

D. The test will be skipped because of timeout

Solution

1. Step 1: Analyze the timeout and sleep duration

   The test has a timeout of 2 seconds but sleeps for 3 seconds, which is longer than allowed.

2. Step 2: Understand test behavior on timeout

   JUnit will stop the test after 2 seconds and mark it as failed due to timeout.

3. Final Answer:

   The test will fail due to timeout after 2 seconds -> Option A

4. Quick Check:

   Sleep longer than timeout causes failure = B [OK]

Hint: Sleep longer than timeout causes fail [OK]

Common Mistakes:

• Thinking test passes despite long sleep
• Assuming test fails immediately without waiting
• Believing test is skipped instead of failed

4. This JUnit 5 test uses @Timeout(1) but does not compile. What is the error?

@Test
@Timeout(1)
void testMethod() {
    // test code
}

medium

A. Missing import for @Timeout annotation

B. Timeout annotation requires a time unit parameter

C. Timeout value must be a string, not an integer

D. Timeout annotation cannot be used on void methods

Solution

1. Step 1: Check @Timeout annotation parameters

   The @Timeout annotation requires both a value and a time unit parameter in JUnit 5.

2. Step 2: Identify missing time unit

   Using @Timeout(1) without specifying the time unit causes a compilation error.

3. Final Answer:

   Timeout annotation requires a time unit parameter -> Option B

4. Quick Check:

   Missing time unit parameter = A [OK]

Hint: Specify time unit with @Timeout [OK]

Common Mistakes:

• Forgetting to specify time unit
• Using @Timeout without time unit
• Thinking @Timeout only works on non-void methods

5. You want to apply a timeout of 500 milliseconds to all test methods in a JUnit 5 test class. Which is the best way to do this?

hard

A. Add @Timeout(value = 500, unit = TimeUnit.MILLISECONDS) on the test class

B. Use Thread.sleep(500) in each test method

C. Set a global timeout property in the JUnit configuration file

D. Add @Timeout(value = 500, unit = TimeUnit.MILLISECONDS) on each test method

Solution

1. Step 1: Understand class-level @Timeout usage

   JUnit 5 allows applying @Timeout at the class level to set a timeout for all test methods inside.

2. Step 2: Compare options for efficiency

   Adding @Timeout on the class is simpler and ensures all tests have the timeout without repeating annotation.

3. Final Answer:

   Add @Timeout(value = 500, unit = TimeUnit.MILLISECONDS) on the test class -> Option A

4. Quick Check:

   Class-level @Timeout applies to all tests = D [OK]

Hint: Put @Timeout on class to affect all tests [OK]

Common Mistakes:

• Adding @Timeout repeatedly on each method
• Trying to set timeout via sleep calls
• Assuming global config sets timeout automatically