How can I prevent stability problems caused by an oscillating system?

When power supplies or other circuit arrangements stabilizing an output parameter by a control loop are tested, two regulators are connected together when applying the electronic load to the UUT. When a phase shift of more than 180° and an amplification >1 are reached by the system, the oscillation condition is true and the system starts to oscillate.
This state is no fault of the electronic load but is unwanted in tests. The oscillating system can be stabilized by interrupting the conditions for the oscillating system.
A capacitor may be connected parallel in series with an resistor to the load input. Sometimes a small MKT capacitor of about 1µF with 1 Ohm of resistance in series is already enough to stabilize the system.
In addition, most of H&H electronic loads have the possibility to set a slower regulation speed (see user manual).