get the measure of
• assess the character or abilities of (someone or something).
• "he's got her measure—she won't fool him"
Similar:
evaluate,
assess,
gauge,
judge,
weigh up,
understand,
fathom,
read,
be wise to,
not be deceived by,
see through,
have someone's number,
not fall for,
know someone's (little) game,
