Question about using a custom container with a test trait

[cassianomonteiro]

I'm looking at the documentation here, but I'm not understanding how to use that custom container to register and get access to my mocks.

For example, my live container is:

extension Container {
  var service: Factory<ServiceProtocol> {
    Factory(self) { ServiceImpl() }.singleton
  }
}

In the live code, I use this to get the instance: Container.shared.service().

I tried to create a custom Container:

public final class TestContainer: SharedContainer {
  @TaskLocal public static var shared = TestContainer()
  public let manager = ContainerManager()
}

extension Trait where Self == ContainerTrait<TestContainer> {
    static var testContainer: ContainerTrait<TestContainer> {
        .init(shared: TestContainer.$shared, container: .init())
    }
}

But then in my test case:

@Suite(.testContainer)
struct CheckoutBackRequestTests {

  @Test
  func myTest async throws {
    let mockService = MockService()
    // How do I register the mock instance?
    TestContainer.shared.service.register { mockService }  // <-- this doesn't work since I don't have a service variable in my TestContainer
    Container.shared.service.register { mockService } // <-- This would be using the regular Container, not the TestContainer, correct?
  }
}

What is the expected usage of a custom container in a test trait?

Thanks in advance!