Add tear down method to handler tests (#262)

Author: Maria Ines Parnisari

python/rpdk/java/templates/init/guided_aws/StubHandlerTest.java

@@ -7,6 +7,7 @@
 import software.amazon.cloudformation.proxy.ProgressEvent;
 import software.amazon.cloudformation.proxy.ProxyClient;
 import software.amazon.cloudformation.proxy.ResourceHandlerRequest;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -15,6 +16,9 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 @ExtendWith(MockitoExtension.class)
 public class {{ operation }}HandlerTest extends AbstractTestBase {
@@ -35,6 +39,12 @@ public void setup() {
         proxyClient = MOCK_PROXY(proxy, sdkClient);
     }
 
+    @AfterEach
+    public void tear_down() {
+        verify(sdkClient, atLeastOnce()).serviceName();
+        verifyNoMoreInteractions(sdkClient);
+    }
+
     @Test
     public void handleRequest_SimpleSuccess() {
         final {{ operation }}Handler handler = new {{ operation }}Handler();