Merge pull request #12838 from etrandafir93/features/BAEL-5813-mono_onSuccess_vs_onNext

BAEL-5813: Mono<> doOnSuccess vs doOnNex

spring-5-webflux-2/src/main/java/onsuccess/Payment.java

@@ -0,0 +1,10 @@
+package onsuccess;
+
+
+public class Payment {
+    private final int amount;
+
+    public Payment(int amount) {
+        this.amount = amount;
+    }
+}

spring-5-webflux-2/src/main/java/onsuccess/PaymentService.java

@@ -0,0 +1,9 @@
+package onsuccess;
+
+public class PaymentService {
+
+    public void processPayment(Payment payment) {
+        System.err.println("Payment processed: " + payment);
+    }
+
+}

spring-5-webflux-2/src/test/java/onsuccess/MonoOnSuccessVsOnNexUnitTest.java

@@ -0,0 +1,67 @@
+package onsuccess;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.verify;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mock;
+
+import reactor.core.publisher.Mono;
+
+class MonoOnSuccessVsOnNexUnitTest {
+
+    @Mock
+    PaymentService paymentService = mock(PaymentService.class);
+
+    @BeforeEach
+    void beforeEach() {
+        reset(paymentService);
+    }
+
+    @Test
+    void givenAPaymentMono_whenCallingServiceOnNext_thenCallServiceWithPayment() {
+        Payment paymentOf100 = new Payment(100);
+        Mono<Payment> paymentMono = Mono.just(paymentOf100);
+
+        paymentMono.doOnNext(paymentService::processPayment)
+            .block();
+
+        verify(paymentService).processPayment(paymentOf100);
+    }
+
+    @Test
+    void givenAnEmptyMono_whenCallingServiceOnNext_thenDoNotCallService() {
+        Mono<Payment> emptyMono = Mono.empty();
+
+        emptyMono.doOnNext(paymentService::processPayment)
+            .block();
+
+        verify(paymentService, never()).processPayment(any());
+    }
+
+    @Test
+    void givenAPaymentMono_whenCallingServiceOnSuccess_thenCallServiceWithPayment() {
+        Payment paymentOf100 = new Payment(100);
+        Mono<Payment> paymentMono = Mono.just(paymentOf100);
+
+        paymentMono.doOnSuccess(paymentService::processPayment)
+            .block();
+
+        verify(paymentService).processPayment(paymentOf100);
+    }
+
+    @Test
+    void givenAnEmptyMono_whenCallingServiceOnSuccess_thenCallServiceWithNull() {
+        Mono<Payment> emptyMono = Mono.empty();
+
+        emptyMono.doOnSuccess(paymentService::processPayment)
+            .block();
+
+        verify(paymentService).processPayment(null);
+    }
+
+}