@NullAndEmptySource in JUnit - Test Execution Trace

Test Overview

This test uses the @NullAndEmptySource annotation in JUnit to run the same test method twice: once with a null input and once with an empty string. It verifies that the method handles both cases correctly by returning false.

Test Code - JUnit 5

JUnit

import static org.junit.jupiter.api.Assertions.assertFalse;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.NullAndEmptySource;

public class InputValidatorTest {

    @ParameterizedTest
    @NullAndEmptySource
    void testIsValidInputWithNullAndEmpty(String input) {
        InputValidator validator = new InputValidator();
        boolean result = validator.isValidInput(input);
        assertFalse(result, "Input should be invalid for null or empty string");
    }
}

class InputValidator {
    public boolean isValidInput(String input) {
        return input != null && !input.isEmpty();
    }
}

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initializes the test class InputValidatorTest	-	PASS
2	Runs parameterized test with input = null	InputValidator instance created; input parameter is null	assertFalse(result) where result = isValidInput(null)	PASS
3	Runs parameterized test with input = "" (empty string)	InputValidator instance created; input parameter is empty string	assertFalse(result) where result = isValidInput("")	PASS
4	Test ends	All parameterized test cases executed	-	PASS

Failure Scenario

Failing Condition: The isValidInput method returns true for null or empty string inputs

Execution Trace Quiz - 3 Questions

What inputs does the @NullAndEmptySource annotation provide to the test method?

A null and empty string

B null and whitespace string

C empty string and whitespace string

D null only

Key Result

Using @NullAndEmptySource in JUnit parameterized tests helps verify that methods correctly handle null and empty inputs, which are common edge cases that can cause bugs if not tested.