Adding snips for documentation pages (#772)

Author: Evanthx

core/src/test/java/io/temporal/samples/nexus/caller/CallerWorkflowJunit5MockTest.java

@@ -16,6 +16,7 @@
 // This is an example of how to unit test Nexus services in JUnit5. The handlers are mocked,
 // so that the caller classes interact with the mocks and not the handler classes themselves.
 
+// @@@SNIPSTART java-nexus-sample-junit5-mock
 public class CallerWorkflowJunit5MockTest {
 
   // Sync Nexus operations run inline in the handler thread — there is no backing workflow to
@@ -77,3 +78,5 @@ public void testEchoWorkflow(
     testEnv.shutdown();
   }
 }
+
+// @@@SNIPEND

core/src/test/java/io/temporal/samples/nexus/caller/CallerWorkflowMockTest.java

@@ -17,6 +17,7 @@
 // This is an example of how to unit test Nexus services in JUnit4. The handlers are mocked,
 // so that the caller classes interact with the mocks and not the handler classes themselves.
 
+// @@@SNIPSTART java-nexus-sample-junit4-mock
 public class CallerWorkflowMockTest {
 
   // Inject a mock EchoClient so sync Nexus operations can be stubbed per test.
@@ -90,3 +91,5 @@ public void testEchoWorkflow() {
     testWorkflowRule.getTestEnvironment().shutdown();
   }
 }
+
+// @@@SNIPEND

core/src/test/java/io/temporal/samples/nexus/caller/NexusServiceJunit5Test.java

@@ -18,6 +18,8 @@
 // This is the path to take when you don't have access to the service implementation so
 // cannot mock it. Since the SampleNexusService itself is mocked,
 // no handlers need to be set up or mocked.
+
+// @@@SNIPSTART java-nexus-service-sample-junit4-mock
 public class NexusServiceJunit5Test {
 
   private final SampleNexusService mockNexusService = mock(SampleNexusService.class);
@@ -103,3 +105,5 @@ public void testEchoWorkflow(
     verifyNoMoreInteractions(mockNexusService);
   }
 }
+
+// @@@SNIPEND

core/src/test/java/io/temporal/samples/nexus/caller/NexusServiceMockTest.java

@@ -17,6 +17,8 @@
 // This is the path to take when you don't have access to the service implementation so
 // cannot mock it. Since the SampleNexusService itself is mocked,
 // no handlers need to be set up or mocked.
+
+// @@@SNIPSTART java-nexus-service-sample-junit4-mock
 public class NexusServiceMockTest {
 
   private final SampleNexusService mockNexusService = mock(SampleNexusService.class);
@@ -102,3 +104,5 @@ public void testEchoCallerWithMockedService() {
     verifyNoMoreInteractions(mockNexusService);
   }
 }
+
+// @@@SNIPEND