Helidon mock documentation

Signed-off-by: tvallin <[email protected]>

Author: tvallin

docs/src/main/asciidoc/mp/testing/testing.adoc

@@ -161,6 +161,41 @@ include::{sourcedir}/mp/testing/TestingSnippets.java[tag=snippet_2, indent=0]
 
 == Mock Support
 
+This section describes how to mock objects using Helidon API and in a second phase, using pure CDI.
+
+=== Helidon Mock Support
+
+Helidon has its own API to use mocking with test classes annotated with `@HelidonTest`.
+
+==== Maven Coordinates
+
+To enable Helidon Mock Support add the following dependency to your project’s pom.xml.
+[source,xml]
+----
+<dependency>
+    <groupId>io.helidon.microprofile.testing</groupId>
+    <artifactId>helidon-microprofile-testing-mocking</artifactId>
+    <scope>test</scope>
+</dependency>
+----
+
+==== API
+
+It consists of one annotation named `@MockBean`, designed to be used on fields and parameters. The implementation
+relies only on CDI and thus it works with either JUnit or TestNG. The annotation has a parameter `answers` used
+to set the default answer for the mocked beans.
+
+==== Example
+
+[source,java]
+.Code sample
+----
+include::{sourcedir}/mp/testing/HelidonMockingSnippets.java[tag=snippet_1, indent=0]
+----
+<1> `service` field annotated with `@MockBean` and `Answers.CALLS_REAL_METHODS` for default answers.
+<2> Test the mocked service with real method response.
+<3> Test the mocked service with modified behavior.
+
 === Mocking objects with pure CDI
 
 CDI can be used to enable mocking, the following example shows how to mock a service and inject it in a JAX-RS resource.

docs/src/main/java/io/helidon/docs/mp/testing/HelidonMockingSnippets.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2024 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.helidon.docs.mp.testing;
+
+import io.helidon.microprofile.testing.junit5.AddBean;
+import io.helidon.microprofile.testing.junit5.HelidonTest;
+import io.helidon.microprofile.testing.mocking.MockBean;
+
+import jakarta.inject.Inject;
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.client.WebTarget;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.Answers;
+import org.mockito.Mockito;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+@SuppressWarnings("ALL")
+class HelidonMockingSnippets {
+
+    // tag::snippet_1[]
+    @HelidonTest
+    @AddBean(MockBeanAnswerTest.Resource.class)
+    @AddBean(MockBeanAnswerTest.Service.class)
+    class MockBeanAnswerTest {
+
+        @MockBean(answer = Answers.CALLS_REAL_METHODS) // <1>
+        private Service service;
+        @Inject
+        private WebTarget target;
+
+        @Test
+        void injectionTest() {
+            String response = target.path("/test").request().get(String.class);
+            assertThat(response, is("Not Mocked")); // <2>
+            Mockito.when(service.test()).thenReturn("Mocked");
+            response = target.path("/test").request().get(String.class);
+            assertThat(response, is("Mocked")); // <3>
+        }
+
+        @Path("/test")
+        public static class Resource {
+
+            @Inject
+            private Service service;
+
+            @GET
+            public String test() {
+                return service.test();
+            }
+        }
+
+        static class Service {
+
+            String test() {
+                return "Not Mocked";
+            }
+
+        }
+    }
+    // end::snippet_1[]
+}