My question is how can we test as a consumer of SaaS solutions APIs if we don't own the producer or the producer does not use Pact. Is there any other way to do contract testing in the scenario ? has anyone implemented CDCT for SaaS solutions ?

It's tough because you can't control it. You could use the CLI verifier but it's likely to be flakey. I'm not sure it's a good scenario for Pact

thanks for your reply