Test Fallback method using sping-cloud-starter-circuitbreaker-resilience4j - spring-boot

Question

public String getAlbumList() {
CircuitBreaker circuitBreaker = circuitBreakerFactory.create("circuitbreaker");
String url = "http://localhost:1234/not-real";
return circuitBreaker.run(() -> restTemplate.getForObject(url, String.class),
throwable -> getDefaultAlbumList());
}
Assume this is my code and "getDefaultAlbumList()" is returning some string "ABCD", and let say my "restTemplate.getForObject(url, String.class)" is going to call some URL which may take more than 5 second, now point is
I want to test that fallback method, how do i test it, how do i mock so that my controller return fallback response.
Thanks

Answer 1

I suppose that you are trying out the example from here: Quick Guide to Spring Cloud Circuit Breaker. So, I copied their service and I introduced a method to pass a null URL. Then I created a test in a spring boot project that verifies if the string value that returns is the fallback string.
#Service
public class AlbumService {
private RestTemplate restTemplate = new RestTemplate();
#Autowired
private CircuitBreakerFactory circuitBreakerFactory;
public String getAlbumList() {
return getAlbumList("https://jsonplaceholder.typicode.com/albums");
}
public String getAlbumList(String url) {
CircuitBreaker circuitBreaker = circuitBreakerFactory.create("circuitbreaker");
return circuitBreaker.run(() -> restTemplate.getForObject(url, String.class),
throwable -> getDefaultAlbumList());
}
// fallback method that reads a default json file
private String getDefaultAlbumList() {
try {
return new String(Files.readAllBytes(
Paths.get(getClass().getClassLoader().getResource("data/fallback-album-list.json").toURI())
));
} catch (Exception e) {
LOGGER.error("error occurred while reading the file", e);
}
return null;
}
}
Then the unit test should test the fallback default json string.
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE, properties = {"server.port=0"})
#ExtendWith(SpringExtension.class)
#DirtiesContext
class AlbumServiceTest {
#Autowired
AlbumService albumService;
#Test
void getAlbumListFallBack() {
String result = albumService.getAlbumList(null);
assertNotNull(result);
assertTrue(result.length() > 0);
assertEquals(
"[\n" +
" {\n" +
" \"userId\": 1,\n" +
" \"id\": 1,\n" +
" \"title\": \"quidem molestiae enim\"\n" +
" },\n" +
" {\n" +
" \"userId\": 1,\n" +
" \"id\": 2,\n" +
" \"title\": \"sunt qui excepturi placeat culpa\"\n" +
" }\n" +
"]",
result);
}
}