Microservices testing: how do you test interactions between services?

testing interactions between microservices feels like a huge challenge. unit tests and integration tests for individual services are fine, but how do you effectively test the contracts and interactions between services? we're looking at contract testing with tools like pact, but it adds another layer of complexity. running end-to-end integration tests against real services in ci takes about 45 minutes just to spin up 8 docker containers, which is slowing us down. service virtualization is an option but it also requires significant setup. what's the right balance between coverage and speed here? how do teams manage robust microservices testing without grinding development to a halt?