Challenge - 5 Problems

🎖️

Fast Test Mastery

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Test your skills under time pressure!

🧠 Conceptual

intermediate

2:00remaining

Why do fast tests encourage developers to run tests more often?

Choose the best reason why fast tests lead to more frequent test runs by developers.

AFast tests give quick feedback, so developers can fix issues immediately without waiting long.

BFast tests use less memory, so they can run on any computer regardless of specs.

CFast tests require fewer lines of code, making them easier to write and understand.

DFast tests automatically find all bugs without needing manual checks.

Attempts:

2 left

❓ Predict Output

intermediate

2:00remaining

What is the output of this JUnit test timing code?

Given the following JUnit test code, what will be printed when the test runs?

JUnit

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class SpeedTest {
    @Test
    void testFast() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(50); // simulate fast test
        long duration = System.currentTimeMillis() - start;
        System.out.println("Test duration: " + duration + " ms");
        assertTrue(duration < 100);
    }
}

ATest duration: 50 ms (approximately), test passes

BTest duration: 150 ms (approximately), test passes

CTest duration: 50 ms (approximately), test fails

DCompilation error due to missing imports

Attempts:

2 left

❓ assertion

advanced

2:00remaining

Which assertion best checks that a fast test runs under 200 ms?

Choose the correct JUnit assertion to verify a test method completes in less than 200 milliseconds.

JUnit

long duration = measureTestDuration(); // returns test duration in ms

AassertEquals(duration, 200, "Test duration mismatch");

BassertTrue(duration < 200, "Test took too long");

CassertFalse(duration > 200, "Test took too long");

DassertNull(duration, "Duration should be null");

Attempts:

2 left

🔧 Debug

advanced

2:00remaining

Why does this test sometimes fail when run with others?

Consider this JUnit test that measures execution time. Sometimes it fails when run with other tests. Why?

JUnit

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class TimingTest {
    @Test
    void testDuration() throws InterruptedException {
        long start = System.currentTimeMillis();
        Thread.sleep(100);
        long duration = System.currentTimeMillis() - start;
        assertTrue(duration < 150, "Test took too long");
    }
}

ASystem.currentTimeMillis() returns a fixed value, so duration is always zero.

BThe assertion is wrong; duration should be greater than 150 ms.

CThread.sleep(100) is not allowed in JUnit tests and causes failure.

DOther tests running in parallel slow down this test, causing duration to exceed 150 ms.

Attempts:

2 left

❓ framework

expert

2:00remaining

How does a fast test suite improve Continuous Integration (CI) pipelines?

Choose the best explanation of how fast tests benefit CI pipelines in software projects.

AFast tests automatically fix bugs during CI runs without developer input.

BFast tests use less disk space in CI servers, preventing storage issues.

CFast tests reduce CI pipeline time, allowing developers to get feedback quickly and merge changes faster.

DFast tests eliminate the need for manual code reviews in CI.

Attempts:

2 left