@Deployment(testable = false)
public static WebArchive deploy() throws URISyntaxException {
    return ShrinkWrap.create(WebArchive.class)
            .addAsLibrary(new File("src/main/webapp/WEB-INF/lib/myResources.jar"), "myResources.jar");
}

@Test
    public void getMyResourceJarStyles() throws MalformedURLException {
        Client client = ClientBuilder.newClient();
        WebTarget target = client.target(URI.create(new URL(base, "styles.css").toExternalForm()));
        Response response = target.request().get();

        assertThat(response.getStatus(), is(equalTo(200)));

        String style = response.readEntity(String.class);
        assertThat(style, startsWith("body {"));
    }

}