To test it properly, you'd need to lift one leg.
But sometimes you can deduce things.
Measuring in-circuit means there may be parallel current paths, and this will result in a lower than expected reading.
How much lower depends on what the parallel current paths are.
If the in-circuit reading is much *higher* than expected, then it's likely that *all* you are reading are the parallel current paths; it's an indication the resistor is open-circuit.
Resistors don't fail often, and when they do it's usually open-circuit with obvious visible charring.