@Autowired, @Component and testing

Question

How would you go about integration testing a spring application that is annotation-configured and component-scanned and does not have an XML configuration at all? I'm hitting a wall with the need to replace production components with testing components without actually resorting to xml configuration or reflection injections to all the @autowired parts.

Example:

interface A {...}

@Component
class AImpl implements A {
    ...
}


interface B {...}

@Component 
class BImpl implements B {
    @Autowired A a;
    ...
}


interface C {...}

class CImpl implements C {
    @Autowired B b;
    ...
}

then in my test I want to use ATestImpl, but I only have access to C (integration testing C).

How would you go about doing that?

Answer 1

Take advantage of @Primary annotation:

@Service
@Primary
public class TestA implements A {
  //...
}

If there is more than one bean implementing A, Spring will prefer the one annotated with @Primary. If you place TestA class in /src/test/java, it will only be picked up during test execution, on normal context startup Spring won't see TestA and use only avaialble AImpl.