Code quality gates in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a code quality gate in JUnit testing?

Choose the best description of what a code quality gate does in the context of JUnit tests.

A It automatically fixes failing tests during the build process.

B It blocks code from merging if tests fail or coverage is below a threshold.

C It generates test data for JUnit tests to improve coverage.

D It runs tests only on the developer's local machine before commit.

💡 Hint

Think about how quality gates help maintain code standards before merging.

Code quality gates enforce rules like passing tests and minimum coverage before code merges, preventing bad code from entering the main branch.

❓ Predict Output

intermediate

JUnit test result with quality gate failure

Given the following JUnit test class, what will be the outcome if a quality gate requires 80% coverage but only 60% is achieved?

JUnit

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

public class CalculatorTest {
    @Test
    void testAdd() {
        assertEquals(5, 2 + 3);
    }
    // No test for subtract method
}

class Calculator {
    int add(int a, int b) { return a + b; }
    int subtract(int a, int b) { return a - b; }
}

A Tests pass but quality gate fails due to insufficient coverage.

B Build fails due to syntax errors in test class.

C Quality gate passes because all tests pass.

D Tests fail because subtract method is not tested.

💡 Hint

Passing tests do not guarantee quality gate success if coverage is low.

Even if all tests pass, the quality gate can fail if coverage thresholds are not met, as in this case where subtract is untested.

❓ assertion

advanced

Which assertion correctly verifies a method throws an exception in JUnit 5?

Choose the correct JUnit 5 assertion to test that calling divide(5, 0) throws ArithmeticException.

JUnit

public class MathUtils {
    public static int divide(int a, int b) {
        return a / b;
    }
}

A assertDoesNotThrow(() -> MathUtils.divide(5, 0));

B assertEquals(ArithmeticException.class, MathUtils.divide(5, 0));

C assertTrue(MathUtils.divide(5, 0) instanceof ArithmeticException);

D assertThrows(ArithmeticException.class, () -> MathUtils.divide(5, 0));

💡 Hint

Look for the method that expects an exception to be thrown.

assertThrows checks that the specified exception is thrown by the code block. Other options either check wrong things or expect no exception.

🔧 Debug

advanced

Identify the cause of quality gate failure in this JUnit test suite

Given this test suite, why does the quality gate fail despite all tests passing?

JUnit

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

public class StringUtilsTest {
    @Test
    void testIsEmpty() {
        assertTrue(StringUtils.isEmpty(""));
    }
    // Missing tests for isNotEmpty method
}

class StringUtils {
    static boolean isEmpty(String s) { return s == null || s.isEmpty(); }
    static boolean isNotEmpty(String s) { return !isEmpty(s); }
}

A Coverage is low because isNotEmpty method is not tested.

B Tests fail due to NullPointerException in isEmpty method.

C Quality gate fails because test method name is incorrect.

D Build fails due to missing import statements.

💡 Hint

Think about what code is not covered by tests.

All tests pass but the quality gate fails because the isNotEmpty method is never tested, lowering coverage below the threshold.

❓ framework

expert

How to integrate a code quality gate with JUnit tests in a CI pipeline?

Which approach correctly integrates JUnit test results and coverage reports to enforce a quality gate in a CI pipeline?

A Use JUnit to generate coverage report without additional tools, then merge code regardless of results.

B Run JUnit tests only locally, then manually check coverage before merging.

C Run JUnit tests, generate coverage report with JaCoCo, then fail build if coverage < threshold.

D Skip tests and rely on manual code review to enforce quality gate.

💡 Hint

Think about automation and tools that measure coverage in CI.

Automated CI pipelines run JUnit tests and use tools like JaCoCo to measure coverage. The build fails if coverage is below the set threshold, enforcing the quality gate.