Imam al-Shafi'i (may Allah have mercy on him) said: "The testimony of neither of them is admissible, and that is because it is part of the disliked idle amusement (lahw) that resembles falsehood; for whoever does this is regarded as foolish and lacking in decency (muru'ah), and whoever accepts this for himself holds (his honour) lightly, even if it is not clearly forbidden."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / Q21003