@Test
  public void alternativeCollectionFormat() throws Exception {
    server.enqueue(new MockResponse().setBody("body"));

    TestInterface api =
        newBuilder().target(TestInterface.class, "http://localhost:" + server.getPort());

    Response response = api.getCSV(Arrays.asList("bar", "baz"));

    assertThat(response.status()).isEqualTo(200);
    // assertThat(response.reason()).isEqualTo("OK");

    // Some HTTP libraries percent-encode commas in query parameters and others
    // don't.
    MockWebServerAssertions.assertThat(server.takeRequest())
        .hasMethod("GET")
        .hasOneOfPath("/?foo=bar,baz", "/?foo=bar%2Cbaz");
  }
Tests client-specific behavior, such as ensuring Content-Length is sent when specified.
java11/src/test/java/feign/http2client/test/Http2ClientTest.java