Custom Arquillian ArquillianResteasyResource application path- Error HTTP method POST is not supported by this URL

My REST API works fine when deployed but my tests are failing using Jersey Arquillian extension:

@Test
@RunAsClient
public void postTest(@ArquillianResteasyResource final WebTarget webTarget) {

    MyRequest request = new MyRequest();

    String response = webTarget.path("/demo").request(MediaType.APPLICATION_JSON)
            .post(Entity.json(request)).readEntity(String.class);

    Assert.assertEquals("OK", response);

}

I get the error:

Error HTTP method POST is not supported by this URL

My JAX-RS programs look OK:

@ApplicationPath("api")
public class JaxRsActivator extends Application {

}

@Path("/demo")
@Stateless
public class DemoResource extends BaseResource {

    @POST
    public Response demo(MyRequest request) {
        return Response.ok().entity("OK").build();
    }
}

The default value for @ArquillianResteasyResource is rest, but my JaxRsActivator is set to api.

To solve it I used:

@ArquillianResteasyResource("api")

To get the complete URI: webTarget.getUri()