@Test
  void matrixParametersAlsoSupportMaps() throws Exception {
    TestInterface api = new TestInterfaceBuilder().target("http://localhost:" + server.getPort());

    server.enqueue(new MockResponse());
    Map<String, Object> properties = new LinkedHashMap<>();
    properties.put("account", "a");
    properties.put("name", "n");

    api.matrixParametersWithMap(properties);
    assertThat(server.takeRequest()).hasPath("/settings;account=a;name=n");
  }
when you must parse a 2xx status to determine if the operation succeeded or not.
core/src/test/java/feign/FeignTest.java