What is the difference between the Hopkinson's test and the Swinburne's test for a DC motor/generator?
Some of the notable differences between Hopkinson's and Swinburne's test include:

In Hopkinson's test we need a pair of both motor and a generator whereas in Swinburne's we need only one.

The temperature rise can be observed in Hopkinson's test because this test is done under full load conditions but since Swinburne's test is done in no-load conditions, we cannot observe the temperature rise.