@ArgumentsSource with custom providers in JUnit - Test Execution Trace

Test Overview

This test uses JUnit's @ArgumentsSource annotation with a custom provider to supply multiple sets of arguments. It verifies that the tested method correctly processes each input and produces the expected output.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.ArgumentsSource;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.params.provider.ArgumentsProvider;
import java.util.stream.Stream;

public class CustomArgumentsSourceTest {

    static class CustomProvider implements ArgumentsProvider {
        @Override
        public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
            return Stream.of(
                Arguments.of(2, 4),
                Arguments.of(3, 9),
                Arguments.of(4, 16)
            );
        }
    }

    @ParameterizedTest
    @ArgumentsSource(CustomProvider.class)
    void testSquareFunction(int input, int expected) {
        int actual = input * input;
        Assertions.assertEquals(expected, actual, "Square calculation failed");
    }
}

Execution Trace - 7 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initialized	-	PASS
2	JUnit identifies @ParameterizedTest with @ArgumentsSource(CustomProvider.class)	Test method 'testSquareFunction' ready to run with arguments from CustomProvider	-	PASS
3	CustomProvider.provideArguments() called to supply test arguments	Stream of Arguments: (2,4), (3,9), (4,16)	-	PASS
4	Test method invoked with input=2, expected=4	Calculating 2 * 2	Assert actual (4) equals expected (4)	PASS
5	Test method invoked with input=3, expected=9	Calculating 3 * 3	Assert actual (9) equals expected (9)	PASS
6	Test method invoked with input=4, expected=16	Calculating 4 * 4	Assert actual (16) equals expected (16)	PASS
7	All parameterized test cases completed	Test run summary available	-	PASS

Failure Scenario

Failing Condition: The actual square calculation does not match the expected value for any input

Execution Trace Quiz - 3 Questions

What does the CustomProvider class do in this test?

A Supplies multiple sets of arguments to the test method

B Runs the test method multiple times automatically

C Defines the test method to be executed

D Checks the assertion results

Key Result

Using a custom ArgumentsProvider with @ArgumentsSource allows flexible and reusable test data provisioning for parameterized tests, improving test coverage and maintainability.