Can Coveo ML Features Be Tested Before They Are Activated?

Yes. You can test Coveo ML features on a test query pipeline before deploying it in production on a community. You can start using the test query pipeline offline and then include it in an A/B testing on real queries (see Testing Query Pipeline Changes). With usage analytics reports, you can then evaluate the Coveo ML features impact by comparing key metrics for the A and B pipelines (see How Do You Measure the Coveo ML Features Impact? and Analyzing the Performance of Pipeline A Vs Pipeline B).