How to test the quality of a current source design
What kind of analyses you can make depends on the tools and models that you have at your disposal.

The minimum would be a corner simulation over process, voltage and temperature where all possible combinations are used to determine the variation of the output current.

Ideally also a Monte-Carlo simulation should be made to see the impact of device mismatch on your design. If possible corner simulation and Monte-Carlo simulation should be combined.