A tensile test is where make a special specimen of whatever material you want to test, and you put it in a tensile testing machine. The machine slowly strains (elongates) the specimen and measures how the specimen responds, ie how much force it goes under. The machine makes a graph of the stress-strain behavior, where stress is force divided by the cross-section area of the specimen.
This is the very finest way to tell an engineer to get lost.
meselfs: "Go tensile test yourself."