CamelBlueprintTestSupport cannot mock a service defined in a concrete class, rather than an interface

Issue

A Camel application for Fuse on Karaf uses Blueprint XML, and has unit tests based on CamelBlueprintTestSupport. The Blueprint XML refers to services defined by interface and by class:

<reference id="foo" interface="org.test.classes.Foo" />

and

<reference id="bar" component-name="foobar" interface="org.test.classes.FooImpl" ext:proxy-method="classes">

Since the services referenced do not exist at test time, the test attempts to mock them, by overriding addServicesOnStartup() and calling:

services.put (Foo.class.getName(), asService(new FooImpl(), null));

and

services.put (FooImpl.class.getName(), asService(new FooImpl(), null));

The first of these works, whilst the second does not – the test does not start because the service is not instantiated.

It is a characteristic of this problem that the Blueprint code does work correctly when the application is deployed on Karaf, despite the test failure.