Thermal test on SMPS in a metal enclosure

Hi,
Do you agree that a proper thermal oven is the way forward...rather than just putting say a resistive heater in the metal enclosure along with the SMPS-under-test....because surely the heater will instigate convection currents in the enclosure which will tend to cool the components down?

What is your definition of a "proper thermal oven "?

My environmental test chamber has controls for setting the temperature and humidity. The range is from -60°C to +170°C and 20% to 95%.

It uses a fan that is constantly moving air between the test chamber and the heating/cooling section. As such, I expect it moves a lot more air than what would happen from convection.