How to check if wkwebview finished loading in UItest

I want to take a screenshot of the app when it loads a html file. However sometimes the wkwebview takes a long time to load the html file.

Currently I have to use sleep(5) to wait for the wkwebview to finish loading.

//uitest.swift

sleep(5)
takeScreenshot()

Is there any way to check if wkwebview finished loading in UItest?

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