How typetest on enclosures or switchboards is done?

I never heard of it, did a search and found this:

Low Voltage Switchgear & Control Gear Type Testing Guide EN60439-1 by TE Connectivity (http://www.buildingdesign.co.uk/elec-technical/tyco-dorman-t1/dorman-smith-guide-to-type-testing.htm)

Thanks.What are the limits and duration of temperature rise,dielectric test,voltage withstand,impulse test etc?

You need to procure the Standard EN60439-1 to answer your questions.

If I can purchase I won't raise the question here. Can you describe the salient features?

No, since I mentioned that I never heard of it, therefore I do not know any details. I did a quick search and gave you a direction to follow.