Possible test utilities for registry-aware-jersey-client?

[sleberknight]

Over time and across various services, we've accumulated some boilerplate code related to code that uses RegistryAwareClient, specifically in tests for code that uses targetForService and which use the DropwizardClientExtension. This is because we need a way to redirect the targetForService call so that it returns the test resource provided to DropwizardClientExtension.

We have typically used a Mockito spy in order to override only the value returned by calls to targetForService, since we need all the other real functionality of the client.

The following provides several different variations I've found recently in several different services. We will need to determine the similarities and differences between them and determine an appropriate feature set for what to provide.

The first example has two methods. The first one creates the RegistryAwareClient with a mock RegistryClient while the second one accepts any RegistryAwareClient that you provide.

@UtilityClass
public class RegistryAwareClientTestHelpers  {

  static RegistryAwareClient newSpyFor(DropwizardClientExtension clientExtension) {
    var client = ClientBuilders.jersey().registryClient(mock(RegistryClient.class)).build();
    return newSpyFor(clientExtension, client);
  }

  static RegistryAwareClient newSpyFor(DropwizardClientExtension clientExtension, 
                                       RegistryAwareClient registryAwareClient) {

    var theSpy = spy(registryAwareClient);
    var baseUri = clientExtension.baseUri();
    var webTarget = theSpy.target(baseUri);
    doReturn(webTarget).when(theSpy).targetForService(any(ServiceIdentifier.class));

    return theSpy;
  }

  // more helpers...

}

Next is an example that lets you specific JAX-RS client request filters:

static RegistryAwareClient newRegistryAwareClientSpy(DropwizardClientExtension clientExtension,
                                                     ClientRequestFilter... clientRequestFilters) {

    var client = ClientBuilders.jersey().registryClient(mock(RegistryClient.class)).build();

    LOG.info("Registering {} filters", clientRequestFilters.length);
    Arrays.stream(clientRequestFilters).forEach(client::register);

    var clientSpy = spy(client);

    var baseUri = clientExtension.baseUri();
    var webTarget = clientSpy.target(baseUri);
    doReturn(webTarget).when(clientSpy).targetForService(any(ServiceIdentifier.class));

    return clientSpy;
}

The last example accepts a URI and the service name, and creates a spied RegistryAwareClient whose targetForService returns the given URI but only for the specific service name.

static RegistryAwareClient newRegistryAwareClientSpy(URI resourceURI, String serviceName) {
    var client = ClientBuilders.jersey().registryClient(mock(RegistryClient.class)).build();
    var clientSpy = spy(client);

    var webTarget = clientSpy.target(resourceURI);

    // should serviceName really be case-insensitive? Seems like it should match exactly.
    doReturn(webTarget).when(clientSpy).targetForService(
        argThat((ServiceIdentifier) serviceId) -> serviceId.getName().equalsIgnoreCase(serviceName)));

    return clientSpy;
}

There are probably others lying around inside various other services but these seemed to be the most common variations (which were almost certainly copied around).

Note that in order to provide test utilities inside the registry-aware-jersey-client JAR, we'd need to change the scope of test dependencies from test to compile scope. Otherwise we'd have to provide a separate test JAR which I'm not too keen on.

[sleberknight]

Also see this gist from some half-baked experimental code I worked on last fall (October 2021):

https://gist.github.com/sleberknight/b4a4bfce7fc6a1860907331d5415f128

[sleberknight]

The gist above tries to be overly generic and allow handling of all the overloaded targetForService methods. A somewhat ugly, but perhaps effective and simpler, alternative would be to simply mock all of them, e.g. modifying the first example:

  static RegistryAwareClient newSpyFor(DropwizardClientExtension clientExtension, 
                                       RegistryAwareClient registryAwareClient) {

    var theSpy = spy(registryAwareClient);
    var baseUri = clientExtension.baseUri();
    var webTarget = theSpy.target(baseUri);
    
    // return same WebTarget no matter which targetForService method is called
    doReturn(webTarget).when(theSpy).targetForService(any(ServiceIdentifier.class));
    doReturn(webTarget).when(theSpy).targetForService(any(ServiceIdentifier.class), any(PortType.class));
    doReturn(webTarget).when(theSpy).targetForService(any(ServiceIdentifier.class), any(PortType.class), any(Function.class));
    doReturn(webTarget).when(theSpy).targetForService(any(String.class));
    doReturn(webTarget).when(theSpy).targetForService(any(String.class), any(PortType.class));


    return theSpy;
  }

[sleberknight]

Might be better to put these utilities in kiwi-beta before putting in this library.

[sleberknight]

Or just put it in here and annotate it with @Beta