UnsatisfiedDependencyException: There was no object available for injection at SystemInjecteeImpl

Forget the InjectableProvider. You don't need it. The problem is that the mock service is not the one being injected. It is the one created by the DI framework. So you are checking for changes on the mock service, which has never been touched.

So what you need to do is bind the mock with the DI framework. You can simply create another AbstractBinder for testing. It can be a simple anonymous one, where you will bind the mock

ResourceConfig config = new ResourceConfig(PricingResource.class);
config.register(new AbstractBinder() {
    @Override
    protected void configure() {
        bind(pricingServiceMock).to(PricingService.class);
    }
});

Here you are simply binding the mocked service. So the framework will inject the mock into the resource. Now when you modify it in the request, the changes will be seen in the assertion

Oh and you still need to do your when(..).then(..) to initialize the data in the mock service. That is also what you are missing

@Test
public void testFindPrices(){
    Mockito.when(pricingServiceMock.findSomething()).thenReturn(list);