The intention of the AGPL is clear in my opinion and not really up for author interpretation. If someone is accessing code on a server (binary or interpreted), they have a right to obtain and modify that source code.
Aside from SaaS testing suites, I do not know of any examples where test code is accessed by users over a network.
It is, thus, 100% OK to use this source code to test a closed source project.
If the GPL had the same added clause as the AGPL, then there would be a serious number of infringing web apps.
The first sentence of the wikipedia page explains it best: "Both versions of the AGPL were designed to close a perceived application service provider "loophole" (the "ASP loophole") in the ordinary GPL, where by using but not distributing the software, the copyleft provisions are not triggered."
No use == no copyleft requirement, and I would hope it's pretty clear that simply by having a piece of AGPL software in the same directory as another piece of software that it is not inherently using it.
