You can also do a diode test, with a suitable DVM with diode mode, on the JFET to find the PN junction between the gate and either the source or drain before connecting it up in this test circuit. For an N channel JFET you should see a diode junction with its cathode on the source or drain, and anode on the gate. The reverse is true for P channel JFETs. The diode junction measured is the body diode. In the above diagram you can see the PN junctions of an N channel JFET compared to a diode.
What an N channel JFET would look like with a DVM.
Between the source and the drain you should see, with the gate at 0V, a resistance something like 20Ω to 1K, both ways with the DVM.
In most circuits, this JFET PN junction will not see diode action, as it is usually reversed biased. The schematic symbols of both show the anode arrowhead, for the P material in these devices.