There are a number of occasions in the Old Covenant (Tanach that are interpreted as God appearing to a person with instruction/direction, which could be considered a test of faith... One that comes readily to mind is the appearance of the three strangers to announce the imminent pregnancy of Sarah to Avraham (Abraham). In Genesis, Chapter 18 we find Abraham sitting in front of his tent in the noonday sun and sees three strangers approaching. but something indicated to Abraham the supernatural aspect of the three... especially One in particular, whom he addresses as LORD as he bows to the ground before the stranger... a title he would not have used for man or angel. At any rate, many conservative Bible scholars give good reasons for believing this is an appearance of the pre-incarnate Yeshua (יֵשׁוּעַ) , whose name from the Hebrew translates as He saves(or He will save).
You could, if you wish, read about it in Genesis Chapter 18, verses 1 to 15. Other such examples exist...