Merge pull request #20137 from ozangunalp/kafka_in_memory_doc_update

docs/src/main/asciidoc/kafka.adoc

@@ -1439,7 +1439,29 @@ To achieve this, you can _switch_ the channels managed by the Kafka connector to
 
 IMPORTANT: This approach only works for JVM tests. It cannot be used for native tests (because they do not support injection).
 
-First, add the following dependency to your application:
+Let's say we want to test the following processor application:
+
+[source, java]
+----
+@ApplicationScoped
+public class BeverageProcessor {
+
+    @Incoming("orders")
+    @Outgoing("beverages")
+    Beverage process(Order order) {
+        System.out.println("Order received " + order.getProduct());
+        Beverage beverage = new Beverage();
+        beverage.setBeverage(order.getProduct());
+        beverage.setCustomer(order.getCustomer());
+        beverage.setOrderId(order.getOrderId());
+        beverage.setPreparationState("RECEIVED");
+        return beverage;
+    }
+
+}
+----
+
+First, add the following test dependency to your application:
 
 [source, xml]
 ----
@@ -1459,8 +1481,8 @@ public class KafkaTestResourceLifecycleManager implements QuarkusTestResourceLif
     @Override
     public Map<String, String> start() {
         Map<String, String> env = new HashMap<>();
-        Map<String, String> props1 = InMemoryConnector.switchIncomingChannelsToInMemory("orders");  // <1>
-        Map<String, String> props2 = InMemoryConnector.switchOutgoingChannelsToInMemory("queue");   // <2>
+        Map<String, String> props1 = InMemoryConnector.switchIncomingChannelsToInMemory("orders");     // <1>
+        Map<String, String> props2 = InMemoryConnector.switchOutgoingChannelsToInMemory("beverages");  // <2>
         env.putAll(props1);
         env.putAll(props2);
         return env;  // <3>
@@ -1472,8 +1494,8 @@ public class KafkaTestResourceLifecycleManager implements QuarkusTestResourceLif
     }
 }
 ----
-<1> Switch the incoming channel "orders" (expecting messages from Kafka) to in-memory.
-<2> Switch the outgoing channel "queue" (writing messages to Kafka) to in-memory.
+<1> Switch the incoming channel `orders` (expecting messages from Kafka) to in-memory.
+<2> Switch the outgoing channel `beverages` (writing messages to Kafka) to in-memory.
 <3> Builds and returns a `Map` containing all the properties required to configure the application to use in-memory channels.
 <4> When the test stops, clear the `InMemoryConnector` (discard all the received and sent messages)
 
@@ -1490,19 +1512,19 @@ class BaristaTest {
 
     @Test
     void testProcessOrder() {
-        InMemorySource<Order> orders = connector.source("orders"); // <2>
-        InMemorySink<Beverage> queue = connector.sink("queue");    // <3>
+        InMemorySource<Order> ordersIn = connector.source("orders");     // <2>
+        InMemorySink<Beverage> beveragesOut = connector.sink("beverages");  // <3>
 
         Order order = new Order();
         order.setProduct("coffee");
         order.setName("Coffee lover");
         order.setOrderId("1234");
 
-        orders.send(order);  // <4>
+        ordersIn.send(order);  // <4>
 
-        await().<List<? extends Message<Beverage>>>until(queue::received, t -> t.size() == 1); // <5>
+        await().<List<? extends Message<Beverage>>>until(beveragesOut::received, t -> t.size() == 1); // <5>
 
-        Beverage queuedBeverage = queue.received().get(0).getPayload();
+        Beverage queuedBeverage = beveragesOut.received().get(0).getPayload();
         Assertions.assertEquals(Beverage.State.READY, queuedBeverage.getPreparationState());
         Assertions.assertEquals("coffee", queuedBeverage.getBeverage());
         Assertions.assertEquals("Coffee lover", queuedBeverage.getCustomer());
@@ -1513,9 +1535,16 @@ class BaristaTest {
 ----
 <1> Inject the in-memory connector in your test class.
 <2> Retrieve the incoming channel (`orders`) - the channel must have been switched to in-memory in the test resource.
-<3> Retrieve the outgoing channel (`queue`) - the channel must have been switched to in-memory in the test resource.
-<4> Use the `send` method to send a message to the `orders` channel. So, the application will process this message.
-<5> Use the `received` method to check the messages produced by the application.
+<3> Retrieve the outgoing channel (`beverages`) - the channel must have been switched to in-memory in the test resource.
+<4> Use the `send` method to send a message to the `orders` channel.
+The application will process this message and send a message to `beverages` channel.
+<5> Use the `received` method on `beverages` channel to check the messages produced by the application.
+
+[IMPORTANT]
+====
+With in-memory channels we were able to test application code processing messages without starting a Kafka broker.
+Note that different in-memory channels are independent, and switching channel connector to in-memory does not simulate message delivery between channels configured to the same Kafka topic.
+====
 
 === Starting Kafka in a test resource