testing has 1 distinct synonym spread across 1 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the act of subjecting to experimental test in order to determine how well something works
“they agreed to end the testing of atomic weapons”
an examination of the characteristics of something
“there are laboratories for commercial testing”
the act of giving students or candidates a test (as by questions) to determine what they know or have learned
Synonyms, antonyms and the broader and narrower relations for testing come from Princeton University’s WordNet. Full sources and licences.