@Test
  void responseLength() {
    server.enqueue(new MockResponse().setBody("test"));
    TestInterface api =
        newBuilder().target(TestInterface.class, "http://localhost:" + server.getPort());

    Integer expected = 4;
    Response response = api.post("");
    Integer actual = response.body().length();
    assertThat(actual).isEqualTo(expected);
  }
Some client implementation tests should override this test if the PATCH operation is
unsupported.
core/src/test/java/feign/client/AbstractClientTest.java