Test execution time analysis in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to measure the execution time of a test method using System.nanoTime().

JUnit

long startTime = System.nanoTime();
// test code here
long endTime = System.nanoTime();
long duration = endTime - [1];
System.out.println("Execution time in nanoseconds: " + duration);

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

ASystem.currentTimeMillis()

BendTime

Cduration

DstartTime

Attempts:

3 left

💡 Hint

Common Mistakes

Subtracting endTime from startTime, which results in negative duration.

Using System.currentTimeMillis() instead of System.nanoTime() for both times.

The duration is calculated by subtracting the start time from the end time. So, duration = endTime - startTime; is correct.

2fill in blank

medium

Complete the code to annotate a JUnit 5 test method that measures execution time.

JUnit

@[1]
void testMethodExecutionTime() {
    // test code
}

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ABeforeEach

BAfterEach

CTest

DDisabled

Attempts:

3 left

💡 Hint

Common Mistakes

Using @BeforeEach or @AfterEach instead of @Test.

Using @Disabled which disables the test.

The @Test annotation marks a method as a test method in JUnit 5.

3fill in blank

hard

Fix the error in the code that tries to assert the test execution time is less than 1 second.

JUnit

long duration = endTime - startTime;
assertTrue(duration [1] 1_000_000_000, "Test took too long");

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A>

B<

C==

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using > which would assert the test took longer than 1 second.

Using == which is too strict and unlikely.

The assertion should check that the duration is less than 1 second (1,000,000,000 nanoseconds), so the operator is <.

4fill in blank

hard

Fill both blanks to correctly calculate and print the execution time in milliseconds.

JUnit

long start = System.nanoTime();
// test code
long end = System.nanoTime();
long durationMs = (end [1] start) [2] 1_000_000;
System.out.println("Execution time in ms: " + durationMs);

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A-

B/

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Multiplying instead of dividing by 1,000,000.

Adding instead of subtracting start from end.

First, subtract start from end to get duration in nanoseconds, then divide by 1,000,000 to convert to milliseconds.

5fill in blank

hard

Fill both blanks to create a map of test names to their execution times in milliseconds, filtering only tests longer than 100 ms.

JUnit

Map<String, Long> slowTests = testTimes.entrySet().stream()
    .filter(e -> e.getValue() [1] 100_000_000)
    .collect(Collectors.toMap(
        e -> e.getKey(),
        e -> e.getValue() [2] 1_000_000, 
        (a, b) -> a, 
        LinkedHashMap::new));

slowTests.forEach((name, time) -> System.out.println(name + ": " + time + " ms"));

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

A>

B/

C*

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > in filter.

Multiplying instead of dividing to convert units.

Filter tests with execution time greater than 100 ms, then convert nanoseconds to milliseconds by dividing by 1,000,000.