how to write unit tests for spring webflux router?

Question

I am having below kind of EntityRouter, now my question is without autowired handler, how can i mock and write junit unit-tests (not-integration) for such endpoint?

Note: with controller, it is simple for me concept wise, as i can mock service which is usually autowired in controller if we are using spring-web-mvc.

public class EntityRouter {

    @Bean
    public RouterFunction<ServerResponse> route(EntityHandler handler) {
        return RouterFunctions
                .route(GET("/getAllEntities").and(accept(MediaType.APPLICATION_JSON)), handler::findAll)
                .andRoute(GET("/getEntity/{id}").and(accept(MediaType.APPLICATION_STREAM_JSON)), handler::findById)
                .andRoute(POST("/createEntity").and(accept(MediaType.APPLICATION_JSON)), handler::save)
                .andRoute(DELETE("/deleteEntity/{id}").and(accept(MediaType.APPLICATION_JSON)), handler::delete);
    }

}

Answer 1

It should be enough if you mock the EntityHandler class:

@Test
public void testRoute() {
    EntityHandler mockHandler = mock(EntityHandler.class);

    RouterFunction<ServerResponse> routerFunction = new EntityRouter().route(mockHandler);

    // Set up a mock request
    ServerRequest request = mock(ServerRequest.class);
    when(request.method()).thenReturn(HttpMethod.GET);
    when(request.path()).thenReturn("/getAllEntities");
    when(request.headers()).thenReturn(new HttpHeaders());

    // Call the router function
    routerFunction.route(request).subscribe();

    // Verify that the correct method on the mock handler was called
    verify(mockHandler).findAll(request);
}

Answer 2

You can use WebTestClient for reactive stream based rest endpoints. You can find some examples here