An example on how to use WebFluxTest to test a Spring Boot WebFlux Controller

AggregateControllerTest.java

package com.blazemeter.dagger.domains.aggregate;

import com.blazemeter.dagger.domains.aggregate.port.AggregateRepository;
import com.blazemeter.dagger.domains.common.CollectionService;
import org.apache.commons.lang3.RandomUtils;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.ArgumentMatchers;
import org.mockito.Mockito;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.context.annotation.Import;
import org.springframework.http.MediaType;
import org.springframework.security.test.context.support.WithMockUser;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.test.web.reactive.server.WebTestClient;
import reactor.core.publisher.Mono;


@WithMockUser
@ExtendWith(SpringExtension.class)
@WebFluxTest(controllers = AggregateController.class)
@Import(CollectionService.class)
class AggregateControllerTest {

    @MockBean
    AggregateRepository repository;

    @Autowired
    private WebTestClient client;

    @Test
    void getIsDataReady() {
        Mockito
            .when(repository.getIsDataReady(ArgumentMatchers.any()))
            .thenReturn(Mono.just(true));

        client.get()
            .uri("/api/aggregate/data-ready?masterId=" + RandomUtils.nextInt())
            .accept(MediaType.APPLICATION_JSON_UTF8)
            .exchange()
            .expectStatus().isOk();
    }
}