Is thinking for a few minutes about an infidel idea (a mistake in a Quranic word) while trying to prove its error, then stopping, seeking forgiveness, and uttering the Two Testimonies, considered an apostasy?

Fleeting thoughts not vocalized by a Muslim are not blameworthy unless they become a firm belief. A Muslim's dislike and fear of such whispers are signs of sound belief and strong faith. This is supported by the Prophet's (peace be upon him) saying: "That is pure faith," and his saying: "Indeed, Allah has pardoned for my nation what their hearts whisper as long as they do not act upon it or speak of it."