General:
* Standard
* Criterion
* Measure
* Yardstick
* Point of reference
* Baseline
* Gauntlet
* Touchstone
More specific:
* For performance: Performance metric, industry standard, best practice, gold standard
* For comparison: Control, reference point, point of comparison
* For testing: Test case, reference test, performance test
The best synonym depends on the specific situation and the intended meaning.