Junit Mock WebClient In webFLux Inside a component

I am trying to write an end to end test I want to invoke my enpoint with WebTestClient which invoke a component which has a a webClient as a property.The problem is I have a NullPointerException when to the Builder even if the injection is ok. This is my test setup

@Mock
private WebClient.Builder webBuilder;

@Mock
WebClient webclient;

@Mock
BidProperties bidProperties;

@InjectMocks
private BidderProcessorService bidderProcessorService;


private BidsResource bidsResource;

@Before
public void setUp() {
    PowerMockito.when(webBuilder.defaultHeader(HttpHeaders.CONTENT_TYPE, "application/json")).thenReturn(webBuilder);
    PowerMockito.when(webBuilder.defaultHeader(HttpHeaders.CONTENT_TYPE, "application/json").build()).thenReturn(webclient);
    bidderProcessorService = PowerMockito.spy(new BidderProcessorService(bidProperties, webBuilder));
    bidsResource=PowerMockito.spy(new BidsResource(bidderProcessorService));
}

and this is my constructor to the service

 */
public BidderProcessorService(BidProperties bidProperties, WebClient.Builder builder) {
    webclient = builder.defaultHeader(HttpHeaders.CONTENT_TYPE, "application/json").build();
    this.bidProperties = bidProperties;
}