Use @WithMockUser (with @SpringBootTest) inside an oAuth2 Resource Server Application

@WithMockUser creates the authentication in SecurityContext. Same applies for with(user("username")).

By default the OAuth2AuthenticationProcessingFilter does not use the SecurityContext, but always build the authentication from the token ("stateless").

You can easily change this behavior be setting the stateless flag in the resource server security configuration to false:

@Configuration
@EnableResourceServer
public class ResourceServerConfiguration implements ResourceServerConfigurer {

    @Override
    public void configure(ResourceServerSecurityConfigurer security) throws Exception {
        security.stateless(false);
    }

    @Override
    public void configure(HttpSecurity http) {}

}

Another option is to extend ResourceServerConfigurerAdapter, but the problem with that is that it comes with configuration that forces all requests to be authenticated. Implementing the interface leaves your main security config unchanged apart from the statelessness.

Of course, set the flag to to false in your test contexts, only.

I had de same issue, and the only way I found was creating a token and using it in the mockMvc perform

mockMvc.perform(get("/resource")
                    .with(oAuthHelper.bearerToken("test"))

And the OAuthHelper:

@Component
@EnableAuthorizationServer
public class OAuthHelper extends AuthorizationServerConfigurerAdapter {

    @Autowired
    AuthorizationServerTokenServices tokenservice;

    @Autowired
    ClientDetailsService clientDetailsService;

    public RequestPostProcessor bearerToken(final String clientid) {
        return mockRequest -> {
            OAuth2AccessToken token = createAccessToken(clientid);
            mockRequest.addHeader("Authorization", "Bearer " + token.getValue());
            return mockRequest;
        };
    }

    OAuth2AccessToken createAccessToken(final String clientId) {
        ClientDetails client = clientDetailsService.loadClientByClientId(clientId);
        Collection<GrantedAuthority> authorities = client.getAuthorities();
        Set<String> resourceIds = client.getResourceIds();
        Set<String> scopes = client.getScope();

        Map<String, String> requestParameters = Collections.emptyMap();
        boolean approved = true;
        String redirectUrl = null;
        Set<String> responseTypes = Collections.emptySet();
        Map<String, Serializable> extensionProperties = Collections.emptyMap();

        OAuth2Request oAuth2Request = new OAuth2Request(requestParameters, clientId, authorities,
                approved, scopes, resourceIds, redirectUrl, responseTypes, extensionProperties);

        User userPrincipal = new User("user", "", true, true, true, true, authorities);
        UsernamePasswordAuthenticationToken authenticationToken =
                new UsernamePasswordAuthenticationToken(userPrincipal, null, authorities);
        OAuth2Authentication auth = new OAuth2Authentication(oAuth2Request, authenticationToken);

        return tokenservice.createAccessToken(auth);
    }

    @Override
    public void configure(final ClientDetailsServiceConfigurer clients) throws Exception {
        clients.inMemory()
                .withClient("test")
                .authorities("READ");
    }

}