How are op-amp gain vs frequency response curves generated?
The test is done with a circuit like this (and this is how analog devices does their AC gain or open loop tests). You could build one of these circuits and make an open loop gain test (with your device in the spot labeled DUT) There are more ways to make this measurement, but this is one of the best.
 


  Figure 5, the ac signal is applied to the DUT input via a 10,000:1
  attenuator. This large value is needed for low-frequency measurements,
  where open-loop gains may be near the dc value. (For example, at a
  frequency where the gain is 1,000,000, a 1-V rms signal would apply
  100 μV at the amplifier input, which would saturate the amplifier as
  it seeks to deliver 100-V rms output). So ac measurements are normally
  made at frequencies from a few hundred Hz to the frequency at which
  the open-loop gain has dropped to unity—or very carefully with lower
  input amplitudes if low-frequency gain data is needed. The simple
  attenuator shown will only work at frequencies up to 100 kHz or so,
  even if great care is taken with stray capacitance; at higher
  frequencies a more complex circuit would be needed.  


Source: http://www.analog.com/en/analog-dialogue/articles/simple-op-amp-measurements.html