I'm starting to adopt contract testing through Pact framework. I've noted that Pact.io contract tests run with JUnit. Our services use TestNG to run unit tests. Do you see any problems or conflicts on still using testNG to run our current unit test suite and use junit to run contract tests exclusively on the same service repository?

Conceptually no, unless there are some strange library conflicts

i'll try running my current suite of unit tests with TestNG and add a verificatiion contract just to check this