conclusive test

By statute the stock record of ownership is usually made the conclusive test of the right to vote.

The panic and the ensuing crisis furnished a conclusive test of the strength and stability of the American labor movement.

But, theories aside, the unsubstantialness of the comet's tail has been put to a conclusive test.

The only conclusive test of death is the setting in of decomposition.

But of course the most conclusive test is by inoculation with the fungus in question.