Over the years, I've run across this type of concern when authoring test suites which validate external system interaction, not just property-based ones. The s

Over the years, I've run across this type of concern when authoring test suites which validate external system interaction, not just property-based ones. The situation you describe appears to be ideal for having test suites which exercise the third-party API in ways the system your team expects to use it, especially if those suites are viewed as executable documentation. Even if others in the organization do not value automated testing (and, yes, this has happened a lot more than I care to remember), time spent on them bring value by having a reference in-house. Key here, IMHO, is regarding these test suites as verification of what the third-party claims in their documentation (if any). It's important to limit time spent on making these tests, as one wants to avoid making a brittle suite which causes non-trivial maintenance costs for the organization. IOW, try not to go too deep down the rabbit hole.