public class CacheUtils {
    private static Map<String, String> cache = new HashMap<>();
}

@WebMvcTest(HelloController.class)
class HelloControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private HelloService helloService;

    @Test
    void sayHello_returnsExpectedMessage() throws Exception {
        given(helloService.getMessage()).willReturn("Hello!");

        mockMvc.perform(get("/api/hello"))
               .andExpect(status().isOk())
               .andExpect(content().string("Hello!"));
    }
}

@GetMapping("/users/{id}")
public ResponseEntity<User> getUser(@PathVariable Long id) {
    User user = userService.findById(id);

    if (user == null) {
        return ResponseEntity.status(HttpStatus.NOT_FOUND).build();
    }

    return ResponseEntity
            .status(HttpStatus.OK)
            .header("Custom-Header", "UserFound")
            .body(user);
}

<configuration>

    <!-- Async wrapper -->
    <appender name="ASYNC_CONSOLE"
              class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="CONSOLE"/>
        <queueSize>5000</queueSize>
        <discardingThreshold>0</discardingThreshold>
        <includeCallerData>false</includeCallerData>
    </appender>

    <!-- Console appender -->
    <appender name="CONSOLE"
              class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>
%d{yyyy-MM-dd HH:mm:ss} %-5level [%thread] %logger - %msg%n
            </pattern>
        </encoder>
    </appender>

    <root level="INFO">
        <appender-ref ref="ASYNC_CONSOLE"/>
    </root>

</configuration>

@RestController
public class MyController {

    @GetMapping("/admin")
    public String admin() {
        return "Admin panel";
    }
}

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
                .antMatchers("/admin").authenticated()
                .anyRequest().permitAll()
            .and()
            .httpBasic();
    }
}

<!-- зависимость -->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

# application.properties
spring.mail.host=smtp.gmail.com
spring.mail.port=587
spring.mail.username=my_email@gmail.com
spring.mail.password=my_password
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true

@Service
public class MailService {

    @Autowired
    private JavaMailSender mailSender;

    public void sendEmail(String to, String subject, String text) {
        SimpleMailMessage message = new SimpleMailMessage();
        message.setTo(to);
        message.setSubject(subject);
        message.setText(text);
        message.setFrom("your_email@gmail.com");

        mailSender.send(message);
    }
}