lm311n test

start with this: http://www.datasheetcatalog.org/datasheet2/c/0hk0a528fi1yzjwj5rxkj21i4wwy.pdf

then try applying a sine wave to the + input and an adjustable dc voltage to the - input.

as the dc input is varied the duty cycle of the square wave output should change.

It depends what test equipment you have - are you in a lab with 'scope, sig. gen. etc, or do you just have a meter?

yes i am in complete lab.

This isn't a thorough test, but will give you a GO/NO-GO:

Set up circuit as shown:

Apply a square wave, about 100Hz, 0 to 4.5V at input A. Output at B should be a square wave, in phase with the input, going from about 0.75V to 5V.

National Semiconductor's datasheet (see here) has application examples and notes. You'll need a breadboard, power supply, etc. to test the IC outside your device. To test within the device (e.g. on a printed circuit board with other stuff), measure inputs with oscilloscope to see if either has AC present, note voltage levels, and check if output corresponds to input levels. Note also that comparators without hysteresis make fine oscillators when both inputs are approximately same level.