DC absorbtion test

When you say an insulator is "good" or "bad", what do you mean? If you mean Resistance, as indicated by the subject line of your posting, then dielectric absorption is not a measure of insulation resistance. It is possible to have almost infinite resistance, but still have lots of dielectric absorption. Whether or not this is "bad" depends on your application. As for AC or DC tests, high enough frequency AC will test dielectric absorption, but it will be hard to separate the effect from pure capacitance. Dielectric absorbtion can be tested for by placing a high DC voltage on the cable, then shorting it out to zero volts briefly, then watching for a delayed rise in voltage after the short is removed. That is dielectric absorbtion. DC tests will only test insulation resistance