Data-Driven tests in JUnit 4 and JUnit Jupiter

SomeClassUnderTest.java

public class SomeClassUnderTest {
    public String someMethodUnderTest(Object input) {
        return switch (input) {
            case Number number -> String.format("%.2f", number.doubleValue());
            case String string -> String.format("%.2f", Double.parseDouble(string));
            case null -> "null";
            default -> input.toString();
        };
    }
}

TestSomeClassUnderTest_JUnit4_withInvalidInput.java

import org.junit.Test;

public class TestSomeClassUnderTest_JUnit4_withInvalidInput {
    private final SomeClassUnderTest sut = new SomeClassUnderTest();

    @Test(expected=Exception.class)
    public void test() {
        sut.someMethodUnderTest("invalid");
    }
}

TestSomeClassUnderTest_JUnit4_withValidInputs.java

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;

import static org.junit.Assert.assertEquals;
import static org.junit.runners.Parameterized.Parameter;
import static org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class TestSomeClassUnderTest_JUnit4_withValidInputs {
    @Parameters(name="when the input is {0}")
    public static Object[][] data() {
        return new Object[][] {
            {"a string", "123", "123.00"},
            {"an integer", 123, "123.00"},
            {"a float", 123.0, "123.00"},
            {"a negative number", -123, "-123.00"},
            {"null", null, "null"},
        };
    }

    @Parameter(0)
    public String variation;

    @Parameter(1)
    public Object input;

    @Parameter(2)
    public String expectedOutput;

    private final SomeClassUnderTest sut = new SomeClassUnderTest();

    @Test
    public void test() {
        var actualOutput = sut.someMethodUnderTest(input);
        assertEquals(variation, expectedOutput, actualOutput);
    }
}

TestSomeClassUnderTest_JUnit5.java

import java.util.stream.Stream;

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.params.provider.Arguments.arguments;

class TestSomeClassUnderTest_JUnit5 {

    static Stream<Arguments> dataProvider() {
        return Stream.of(
            arguments("a string", "123", "123.00"),
            arguments("an integer", 123, "123.00"),
            arguments("a float", 123.0, "123.00"),
            arguments("a negative number", -123, "-123.00"),
            arguments("a null", null, "null")
        );
    }

    private final SomeClassUnderTest sut = new SomeClassUnderTest();

    @DisplayName("valid inputs")
    @ParameterizedTest(name = "when the input is {0} {1} should be ''{2}''")
    @MethodSource("dataProvider")
    void validInputs(String variation, Object input, String expectedOutput) {
        var actualOutput = sut.someMethodUnderTest(input);
        assertEquals(expectedOutput, actualOutput);
    }

    @Test
    void invalidInput() {
        assertThrows(Exception.class, () -> sut.someMethodUnderTest("invalid"));
    }

}