Added test and some fixes

spring-boot-modules/spring-boot-crud/src/test/java/com/baeldung/crud/UserControllerUnitTest.java

@@ -28,6 +28,11 @@ public class UserControllerUnitTest {
         userController = new UserController(mockedUserRepository);
     }
 
+    @Test
+    public void whenCalledIndex_thenCorrect() {
+        assertThat(userController.showUserList(mockedModel)).isEqualTo("index");
+    }
+
     @Test
     public void whenCalledshowSignUpForm_thenCorrect() {
         User user = new User("John", "john@domain.com");