@Test
  void queryParamsAreRespectedWhenBodyIsEmpty() throws InterruptedException {
    final JaxRsTestInterface testInterface = buildTestInterface();

    server.enqueue(new MockResponse().setBody("foo"));
    server.enqueue(new MockResponse().setBody("foo"));

    assertThat(testInterface.withBody("foo", "bar")).isEqualTo("foo");
    final RecordedRequest request1 = server.takeRequest();
    assertThat(request1.getPath()).isEqualTo("/withBody?foo=foo");
    assertThat(request1.getBody().readString(StandardCharsets.UTF_8)).isEqualTo("bar");

    assertThat(testInterface.withoutBody("foo")).isEqualTo("foo");
    final RecordedRequest request2 = server.takeRequest();
    assertThat(request2.getPath()).isEqualTo("/withoutBody?foo=foo");
    assertThat(request2.getBody().readString(StandardCharsets.UTF_8)).isEqualTo("");
  }
Tests client-specific behavior, such as ensuring Content-Length is sent when specified.
hc5/src/test/java/feign/hc5/ApacheHttp5ClientTest.java