Types aren’t just documentation — they’re contracts the compiler enforces. Want to be sure your utility types do exactly what you expect?

• 🔍 Use type-level assertions to verify correctness
• 🔄 Test for exact matches and meaningful differences
• 📌 Catch edge cases before they hit runtime
• 🧠 Build confidence in your type transforms, even the tricky ones
• 📁 Keep type tests side-by-side for clear red flags in your IDE

When your types test themselves, refactors become less risky and more fun.

📎 Full article → https://javascript.plainenglish.io/type-safety-under-control-reliable-utility-type-checks-in-2025-1ea875dae8af