如何为R2DBC DatabaseClient编写JUnit Mock类并修复报错

在Spring Boot应用中，我通过R2DBC的DatabaseClient实现了一个Repository类，核心数据库操作代码如下：

return client.sql(sqlToSearch)
        .bind("alternateCodeType", alternateCodeType)
        .bind("alternateCode", alternateCode)
        .map(locationR2DBCMapper::apply).one();

其中locationR2DBCMapper是自定义的BiFunction映射类，代码如下：

public class LocationR2DBCMapper implements BiFunction<Row, Object, Location> {

    @Override
    public Location apply(Row row, Object o) {
        if(row.get(0)!=null)
        {
            Location location = new Location();
            location.setId(row.get("location_id", Long.class));
            location.setLocationName(row.get("location_name", String.class));
            location.setLocationType(row.get("location_type", String.class));
            location.setProjectionMsg(row.get("projection_msg", String.class));
            location.setIsFacility(row.get("is_facility",Boolean.class));
            return location;
        }
        else {
            return new Location();
        }
    }
}

我想为这个Repository类编写JUnit测试用例，Mock上述数据库调用。尝试的Mock代码如下：

@BeforeEach
void setUp() {
    databaseClientMock = Mockito.mock(DatabaseClient.class);

    locationR2DBCMapperMock = Mockito.mock(LocationR2DBCMapper.class);

    DatabaseClient databaseClientMock = mock(DatabaseClient.class);
    DatabaseClient.GenericExecuteSpec executeSpecMock = mock(DatabaseClient.GenericExecuteSpec.class);

    Mono<Location> monoResultMock = mock(Mono.class);

    locationCustomRepositoryImplMock = new LocationCustomRepositoryImpl(databaseClientMock,locationR2DBCMapperMock);
}

@Test
public void getLocationByLocationTypeTest()
{
    RowsFetchSpec<?> rowsFetchSpecMock = mock(RowsFetchSpec.class);
    when(databaseClientMock.sql(anyString())).thenReturn(executeSpecMock);
    when(executeSpecMock.map(Mockito.any(BiFunction.class))).thenReturn(rowsFetchSpecMock);
    Flux<Object> resultFluxMock = Flux.empty(); // Replace this with your own Flux instance
    when(rowsFetchSpecMock.all()).thenReturn(resultFluxMock);

    //Mockito.when(databaseClientMock.sql(anyString())).thenReturn(Flux.just(Location.builder().locationName("someName").id(Long.valueOf(123)).build()));
}

但在when(rowsFetchSpecMock.all()).thenReturn(resultFluxMock)这一行报错，提示“Cannot resolve method 'thenReturn(Flux