Mockito: method check was called using a function parameter

Question

I have a simple scenario in which I try to check some behavior when calling a method (i.e. that a certain method was called with the given parameter, the function pointer in this script). The following are my classes:

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);

        AppBootStrapper bootStrapper = context.getBean(AppBootStrapper.class);
        bootStrapper.start();
    }
}

@Component
public class AppBootStrapper {
    private NetworkScanner networkScanner;
    private PacketConsumer packetConsumer;

    public AppBootStrapper(NetworkScanner networkScanner, PacketConsumer packetConsumer) {
        this.networkScanner = networkScanner;
        this.packetConsumer = packetConsumer;
    }

    public void start() {
        networkScanner.addConsumer(packetConsumer::consumePacket);
        networkScanner.startScan();
    }
}

@Component
public class NetworkScanner {
    private List<Consumer<String>> consumers = new ArrayList<>();

    public void startScan(){
        Executors.newSingleThreadExecutor().submit(() -> {
            while(true) {
                // do some scanning and get/parse packets
                consumers.forEach(consumer -> consumer.accept("Package Data"));
            }
        });
    }

    public void addConsumer(Consumer<String> consumer) {
        this.consumers.add(consumer);
    }
}

@Component
public class PacketConsumer {
    public void consumePacket(String packet) {
        System.out.println("Packet received: " + packet);
    }
}

@RunWith(JUnit4.class)
public class AppBootStrapperTest {

    @Test
    public void start() throws Exception {
        NetworkScanner networkScanner = mock(NetworkScanner.class);
        PacketConsumer packetConsumer = mock(PacketConsumer.class);
        AppBootStrapper appBootStrapper = new AppBootStrapper(networkScanner, packetConsumer);

        appBootStrapper.start();

        verify(networkScanner).addConsumer(packetConsumer::consumePacket);
        verify(networkScanner, times(1)).startScan();
    }
}

I want to verify that bootStrapper has indeed performed the correct configuration by registering the consumer of the package (there may be other users registered later, but this is necessary), and then called startScan. When you run the test case, you receive the following error message:

Argument(s) are different! Wanted:
networkScanner bean.addConsumer(
    com.spring.starter.AppBootStrapperTest$$Lambda$8/438123546@282308c3
);
-> at com.spring.starter.AppBootStrapperTest.start(AppBootStrapperTest.java:24)
Actual invocation has different arguments:
networkScanner bean.addConsumer(
    com.spring.starter.AppBootStrapper$$Lambda$7/920446957@5dda14d0
);
-> at com.spring.starter.AppBootStrapper.start(AppBootStrapper.java:12)

Due to the exception, obviously, the function pointers do not match.

? - , ? PacketConsumer , , , , , , , .

, .

Answer 1

Java " "; :

networkScanner.addConsumer(packetConsumer::consumePacket);

Java ():

networkScanner.addConsumer(new Consumer<String>() {
  @Override void accept(String packet) {
    packetConsumer.consumePacket(packet);
  }
});

AppBootStrapper$$Lambda$7. ( ) equals, , , AppBootStrapperTest$$Lambda$8. , .

static final Consumer<String>, ; . - .

, , verify(packetConsumer, atLeastOnce()).consumePacket(...), , , . consumePacket, addConsumer.

. SO.