1990 camry seat belt question

hello, my 1990 camry automatic seatbelts are working fine, but my question is: once the seat belt slides into position, and is resting
snugly over your chest area, isn't the seat belt supposed to lock when you tug on it hard, simulating an accident? i'm conserned that it is not working and want to know if i need to replace a part. thanks!
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