  Suppose that $X = \Spec R$ is an $F$-finite normal variety in characteristic
$p > 0$. In this paper we show that the big test ideal $\tau_b(R) = \tld
\tau(R)$ is equal to $\sum_{\Delta} \tau(R; \Delta)$ where the sum is over
$\Delta$ such that $K_X + \Delta$ is $\bQ$-Cartier. This affirmatively answers
a question asked by various people, including Blickle, Lazarsfeld, K. Lee and
K. Smith. Furthermore, we have a version of this result in the case that $R$ is
not even necessarily normal.
