I have a config class `AppConfig` to receive environment variables and use them inside service `MyService`

```
// application.yml
app-config:
  env-var1: ${ENV_VAR1:}
  env-var2: ${ENV_VAR2:}
  env-var3: ${ENV_VAR3:}
  env-var4: ${ENV_VAR4:}
  env-var5: ${ENV_VAR5:}

// AppConfig.java
@Data
@EnableConfigurationProperties
@ConfigurationProperties(value = "app-config")
public class AppConfig {
    private String envVar1;
    private String envVar2;
    private String envVar3;
    private String envVar4;
    private String envVar5;
}

// MyService.java
@Slf4j
@Service
public class MyService {
    @Autowired
    AppConfig appConfig;

    public void doSomething() {
        log.info(appConfig.getEnvVar1());
        log.info(appConfig.getEnvVar2());

        // business logic controlled by appConfig.envVar1 and appConfig.envVar2
        // other variables not used
    }
}

```

Now I am writing unit test for `MyService`

```
// MyServiceTest.java
@SpringBootTest
class MyServiceTest {
    @Autowired
    AppConfig appConfig;

    @Autowired
    MyService myService;

    @BeforeEach
    void setUp() {
        // reset override
    }

    @AfterEach
    void tearDown() {
        // reset override
    }

    @Test
    void doSomething_envVar1() {
        // override appConfig.envVar1 only

        myService.doSomething()
    }

    @Test
    void doSomething_envVar2() {
        // override appConfig.envVar2 only

        myService.doSomething()
    }
}

```

How can I override only one variable inside `AppConfig` in one test only (and reset it after the test)?