This is the 3551st most frequent Japanese word.
見事
"見事" means "splendid," "admirable," or "excellent."
Here, 見事 is used as an adjective to describe the excellence of his performance.
彼の演技は見事だった。
His performance was splendid.
In this sentence, 見事に functions as an adverb to emphasize the impressive manner in which the test was passed.
見事にテストに合格しました。
I passed the test magnificently.
Here, 見事さ is derived from 見事 as a noun, highlighting the quality of magnificence.