src/test/java/org/apache/commons/text/CasedStringTest.java

package org.apache.commons.text;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;

import static org.junit.jupiter.api.Assertions.assertEquals;

public class CasedStringTest {

    private static String expectedValue(CasedString.StringCase stringCase) {
        switch (stringCase) {
            case Camel:
                return "HelloWorld";
            case Kebab:
                return "Hello-World";
            case Phrase:
                return "Hello World";
            case Snake:
                return "Hello_World";
            case Dot:
                return "Hello.World";
            default:
                throw new RuntimeException("Unsupported StringCase: " + stringCase);
        }
    }

    @ParameterizedTest
    @MethodSource("conversionProvider")
    public void testConversions(CasedString underTest) {
        for (CasedString.StringCase stringCase : CasedString.StringCase.values()) {
            assertEquals(expectedValue(stringCase), underTest.toCase(stringCase), () -> "failed converting to " + stringCase);
        }
    }

    private static Stream<Arguments> conversionProvider() {
        List<Arguments> lst = new ArrayList<>();
        for (CasedString.StringCase stringCase : CasedString.StringCase.values()) {
            lst.add(Arguments.of(new CasedString(stringCase, expectedValue(stringCase))));
        }
        return lst.stream();
    }
}