Testing resistors in circuit

[thenewguy]

I am hoping someone could tell me if resistors can be tested while still in the circuit or must they be disconnected at one end, like a capacitor, to remove them from the circuit? I finished recapping a Philco 47-1230 and need to move on to the next step in the troublshooting. I know, I should have tested the resistors as I proceeded with the recap. Won't do that again! I have gone through and tested a dozen or so of the easy to get at ones, just as a experiment, and some test within spec, a few are way off, and one was open. I just don't know if I can trust my readings if the resistors are still connected. Also, of the ones that test out of spec the resistance has gone up, sometimes as much as twice the rating. Is it typical for a bad resistor to increase in ohms, or can they go either way? Are there any good methods for doing this? Thanks