Spring WebFluxTest

Goal

Test web layer of a super simple sample application with WebFluxTest.

Steps

Step 1 : Create the web endpoint

In this sample application there is only one endpoint returning some information about a user. We handle two case :

We find the user : ServerResponse.ok()
We didn't find the user : ServerReponse.notFound()

@Configuration
class UserAccountWebConfiguration {

    private Mono<ServerResponse> findUserInfo(ServerRequest serverRequest, UserAccountFacade userAccountFacade) {

        return userAccountFacade.findUserInfo(serverRequest.pathVariable("userId"))
                .flatMap(userInfoDto -> ServerResponse.ok()
                        .contentType(MediaType.APPLICATION_JSON)
                        .body(Mono.just(userInfoDto), UserInfoDto.class))
                .switchIfEmpty(ServerResponse.notFound().build());
    }

    @Bean
    RouterFunction<ServerResponse> route(UserAccountFacade userAccountFacade) {
        return RouterFunctions.route()
                .GET("/info/{userId}", serverRequest -> findUserInfo(serverRequest, userAccountFacade))
                .build();
    }
}

Step 2 : Create a facade

The project goal is to show how to use WebFluxTest, so we just create a fake facade that return hard coded data. (On a real application we could have a database and use a spring Repository)

public class UserAccountFacade {

    public Mono<UserInfoDto> findUserInfo(String userId) {
        return Mono.just(new UserInfoDto("hardCodedName", "hardCodedCity"));
    }
}

Step 3 : Create a basic DTO

@Data
@AllArgsConstructor
@NoArgsConstructor
public class UserInfoDto {
    private String name;
    private String city;
}

Step 4 : Create test cases

Annotate the test class with @WebFluxTest
Import our web configuration class
Autowire the WebTestClient, needed to make request
MockBean our Facade, needed to test our web layer as a black box, we want to choose what the facade return to test all case

@WebFluxTest
@Import(UserAccountWebConfiguration.class)
class UserAccountWebConfigurationTest {

    @Autowired
    private WebTestClient webTestClient;

    @MockBean
    private UserAccountFacade userAccountFacade;
}

We create a first test case to check the case where we correctly find the user. So we use Mockito to set what the method findUserInforeturn, on this test it return some fake user info.

We then make the request and specify what we expect :

There is a GET endpoint at /info/{userId}
The server respond with status code isOk()
The server respond with header APPLICATION_JSON
The body can be mapped to a UserInfoDto object
The UserInfoDto returned is what we expect

At the end on this test we also check that the method findUserInfo is called once.

    @Test
    void should_find_user_info() {
        String userId = "randomUserId";

        UserInfoDto expectedUserInfoDto = new UserInfoDto("Anthony", "Paris");

        when(userAccountFacade.findUserInfo(userId)).thenReturn(
                Mono.just(expectedUserInfoDto)
        );

        webTestClient.get().uri("/info/" + userId)
                .accept(MediaType.APPLICATION_JSON)
                .exchange()
                .expectStatus().isOk()
                .expectHeader().contentType(MediaType.APPLICATION_JSON)
                .expectBody(UserInfoDto.class)
                .value(userInfoDto -> assertEquals(expectedUserInfoDto, userInfoDto));

        verify(userAccountFacade, times(1)).findUserInfo(userId);
    }

In our next test case we will check for the case where we didn't find the user, so as before we set what findUserInfo return and make the request but this time we expect the server will respond with status code isNotFound().

    @Test
    void should_not_find_user_info() {
        String userId = "randomUserId";

        when(userAccountFacade.findUserInfo(userId)).thenReturn(Mono.empty());

        webTestClient.get().uri("/info/" + userId)
                .accept(MediaType.APPLICATION_JSON)
                .exchange()
                .expectStatus().isNotFound();

        verify(userAccountFacade, times(1)).findUserInfo(userId);
    }