How do you perform testing of the server-side of your applications?

Server-side testing typically includes several levels:

• Unit tests — test individual methods and classes in isolation from external dependencies. Frameworks like JUnit, Mockito are used.
• Integration tests — test the interaction between components, such as controllers, services, and repositories together. Spring Test, Testcontainers are often used to set up a test database.
• End-to-End tests — test the entire system, including APIs. Tools like Postman, REST-assured, or Selenium can be used for UI testing.

Example of a unit test in Java using JUnit and Mockito:

@RunWith(MockitoJUnitRunner.class)
public class UserServiceTest {
    @Mock
    private UserRepository userRepository;

    @InjectMocks
    private UserService userService;

    @Test
    public void testGetUserById() {
        User user = new User(1L, "John");
        Mockito.when(userRepository.findById(1L)).thenReturn(Optional.of(user));

        User result = userService.getUserById(1L);
        assertEquals("John", result.getName());
    }
}

It is important to automate tests and run them in CI/CD for server stability.