1. A method for filtering network nodes, from a set of network nodes within a network, to implement policy-based testing on a reduced set of network nodes, the method comprising: identifying the set of network nodes within the network; generating the reduced set of network nodes, from the set of network nodes within the network, based on a testing policy that specifies at least one policy rule and a threshold number of network nodes to which testing is to be limited, wherein the generating the reduced set of network nodes includes: initially filtering, from the set of network nodes, those network nodes that are endpoints of the network; and subsequently performing iterations of filtering network nodes from the set of network nodes to generate the reduced set of network nodes, wherein the iterations are performed until the reduced set of network nodes is within the threshold number of network nodes, wherein a given iteration of the filtering includes: determining filter criteria from the at least one policy rule; and filtering network nodes from the set of network nodes based on the filter criteria; and invoking a network test scheme, including one or more network tests, that is compliant with the testing policy, wherein the one or more network tests are performed on the reduced set of network nodes.