MockitoBehaviorTest.java

MockitoBehaviorTest.java

public class MockitoBehaviorTest {

  interface Registry {
    void register(Double amount);
  }

  class PaymentProcessingListener {

    private final Registry registry;

    PaymentProcessingListener(Registry registry) {
      this.registry = registry;
    }

    public void onPaymentProcessed(Double amount) {
      if (amount == 0d) {
        return;
      }

      registry.register(amount);
    }
  }

  @Test
  public void processRegularPayment() {


    final Registry registry = mock(Registry.class);

    PaymentProcessingListener listener = new PaymentProcessingListener(registry);
    listener.onPaymentProcessed(20d);

    verify(registry).register(20d);
  }

  @Test
  public void zeroPaymentsAreNotRegistered() {
    Registry registry = mock(Registry.class);

    PaymentProcessingListener listener = new PaymentProcessingListener(registry);

    listener.onPaymentProcessed(0d);

    verifyZeroInteractions(registry);
  }
}