Often one 'knob' or variable is plotted on one axis against another knob or variable on another axis, producing a two-dimensional graph. This allows the test engineer to visually observe the operating ranges of the device under test. This process of varying the conditions and inputs to the component or system may sometimes be referred to as 'shmooing' but more officially known as electrical testing or qualification. Automatic test equipment often contains software features that allow automated shmooing of a part.