Hi, I am learning the pact-jvm framework by rewriting some of our existing wiremock tests. I’ve noticed that in our wiremock tests, multiple services are mocked in a single test. So in pact-jvm terms, that would be a multiprovider test: https://docs.pact.io/implementation_guides/jvm/consumer/junit5#using-multiple-providers-in-a-test-425. Ive followed the instructions and I get the test running, however I’ve ran into problems when defining mock provider ports in case a multiprovider test. I assume that you have to run a different instance of mockserver for each provider, so that each provider will have their own contract. By default a random port is used for each mockserver instance launched during a test. However our application is configured to call the provider by a fixed port. In case of a single provider test, this would be resolved using “port = 1234” in the @PactTestFor annotation:

@Test
@PactTestFor(providerName = "provider1", port = "1234")
public void example(MockServer provider1mock) {
    ...
}

However, when I do this in a multiprovider test:

@Test
@PactTestFor(pactMethods = {"createProvider1Pact", "createProvider2Pact"}, port = "1234")
public void example(@ForProvider("provider1") MockServer provider1mock, @ForProvider("provider2") MockServer provider2mock) {
   ...
}

I get an “address already in used” exception. Which is logical since I instantiate 2 instances of mockserver, and only provide 1 port. It tries to launch both on the same port. However I have found no way of specifying which mockserver should use which port. Is there a way to do this? I could not find anything in the documentation or source code, though I am unfamiliar with kotlin, I may have missed something. I tried making a subclass of MockServer and set the port myself, but then I ran into injection/instantiation issues with my new class. Alternatively, i have also not found a way to let the application use whatever random port is chosen for the mock.

Hi, yeah from what I know from working with the jvm is the only way to be able to force it to use a certain port is to explicitly set the lower and upper port values. If the port the APIs use is a variable, it might be possible to override/set this value depending on what your tech stack is. So when you send request to make a provider, it response with the port number. Can use that to then set your variables. Though my experience is with the jdk 8 implementation 🙂

hmm I did not know you could set port lower and upper values. But I think that wont work either. If I just create a range of 2 ports: 4000-4001, then theres still no guarantee that provider 1 will always get 4000 and provider 2 will get 4001?

-l 4000 and -u 4000

will set it to one port. So would have to spin up the jvm 2 times with different ports in order to force it to only give you a pact provider server running on an explicit port.

Doesnt spinning up 2 jvms (somehow) scream “there must be or should be a better way to do this”? Is my usecase that unordinary?

Again, see if can adapt the code, capture the API response from the jvm when create the server. Then use that value to set the port of your solution 🫠 If application is too port dependent then I would raise this as a configuration issue. Else, suggestion above will mean you would still be able to set the ports. Otherwise make a PR I guess to make it do what you want.