I have a relationship between two components/microservices where component A sends events by HTTP to component B. In a traditional pact HTTP consumer/provider pattern, A is the consumer of B since A is sending the request and B is responding. However, in this case, B is the real consumer of the events that A provides.
Is there a way of implementing the consumer/provider tests so that the consumer test can be written on the receiving side (B) rather than on the sending side?
I have seen that message pacts have been introduced which sounds like it could be used in this scenario but I haven't seen any easy to understand examples of how this is implemented and if it can be used in conjunction with HTTP like in my scenario.
I'm using pact-jvm-junit.
You've outlined to two senses in which the term consumer/provider can be used - the HTTP consumer/provider pair and the consumer/provider of the data itself.
Pact only uses the HTTP consumer/provider sense of the words, because you can't really set up the mock in reverse. You can still use Pact exactly the same way you would normally though - in fact, the first project that used Pact was one where the data flowed from the javascript client to the backend server.
Most HTTP consumer/provider pairs have bi-directional data flow anyway. It's a rare app that is read only. Rather than thinking of it as "how do I, as the consumer of the information, wish to receive the data", think of it as saying "how do I, as the sender of this data, wish to transfer it to the recipient?".