  Jim Agler revolutionized the area of Pick interpolation with his realization
theorem for what is now called the Agler-Schur class for the unit ball in
$\mathbb C^d$. We discuss an extension of these results to algebras of
functions arising from test functions and the dual notion of a family of
reproducing kernels, as well as the related interpolation theorem. When working
with test functions, one ideally wants to use as small a collection as
possible. Nevertheless, in some situations infinite sets of test functions are
unavoidable. When this is the case, certain topological considerations come to
the fore. We illustrate this with examples, including the multiplier algebra of
an annulus and the infinite polydisk.
