Review Summary

Your implementation meets all core task requirements and works correctly. All five text cases (SNAKE, KEBAB, CAMEL, PASCAL, UPPER) are properly supported, URL parsing uses the specified approach with split('?') and URLSearchParams, validation returns the exact error messages required, and responses include all mandatory fields (originalCase, targetCase, originalText, convertedText). One minor improvement: while res.statusMessage defaults to "OK" in Node.js, explicitly setting res.statusMessage = 'OK' would fully align with the requirement specification. This is a non-blocking cosmetic issue and does not affect functionality.

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