Iterator<String> iterator = singletonList("foo").iterator();
    assertEquals("foo", getOnlyElement(iterator, "bar"));
  }

  public void testGetOnlyElement_withDefault_empty() {
    Iterator<String> iterator = emptyIterator();
    assertEquals("bar", getOnlyElement(iterator, "bar"));
  }

  public void testGetOnlyElement_withDefault_empty_null() {
    Iterator<String> iterator = emptyIterator();

  public void testTreeMapDerived() {
    TreeMap<Derived, Integer> map = Maps.newTreeMap();
    assertEquals(emptyMap(), map);
    map.put(new Derived("foo"), 1);
    map.put(new Derived("bar"), 2);
    assertThat(map.keySet()).containsExactly(new Derived("bar"), new Derived("foo")).inOrder();
    assertThat(map.values()).containsExactly(2, 1).inOrder();
    assertThat(map.comparator()).isNull();
  }

  public void testTreeMapNonGeneric() {

                callCount.incrementAndGet();
                startSignal.await();
                return result;
              }
            });

    List<Object> resultArray = doConcurrentGet(cache, "bar", count, startSignal);

    assertThat(callCount.get()).isEqualTo(1);
    for (int i = 0; i < count; i++) {
      assertWithMessage("result(%s) didn't match expected", i)
          .that(resultArray.get(i))

    assertThat(url.queryParameterValues("bar")).isEqualTo(listOf(null as String?))
    assertThat(url.queryParameterValues("baz")).isEqualTo(listOf(null as String?))
  }

  @Test
  fun queryParametersWithEmptyValues() {
    val url = parse("http://host/?foo=&bar=&baz=")
    assertThat(url.querySize).isEqualTo(3)
    assertThat(url.queryParameterNames).containsExactlyInAnyOrder("foo", "bar", "baz")

    assertThat(pushedRequest.requestLine).isEqualTo("GET /foo/bar HTTP/2")
    assertThat(pushedRequest.headers["foo"]).isEqualTo("bar")
  }

  @Test
  fun serverSendsPushPromise_HEAD() {
    val pushPromise =
      PushPromise(
        "HEAD",
        "/foo/bar",
        headersOf("foo", "bar"),
        MockResponse(code = 204),
      )
    server.enqueue(

                callCount.incrementAndGet();
                startSignal.await();
                return result;
              }
            });

    List<Object> resultArray = doConcurrentGet(cache, "bar", count, startSignal);

    assertThat(callCount.get()).isEqualTo(1);
    for (int i = 0; i < count; i++) {
      assertWithMessage("result(%s) didn't match expected", i)
          .that(resultArray.get(i))

  public void testTreeMapDerived() {
    TreeMap<Derived, Integer> map = Maps.newTreeMap();
    assertEquals(emptyMap(), map);
    map.put(new Derived("foo"), 1);
    map.put(new Derived("bar"), 2);
    assertThat(map.keySet()).containsExactly(new Derived("bar"), new Derived("foo")).inOrder();
    assertThat(map.values()).containsExactly(2, 1).inOrder();
    assertThat(map.comparator()).isNull();
  }

  public void testTreeMapNonGeneric() {

    class Bar<T> {}
    class SubBar<T> extends Bar<T> {
      @Keep Bar<T> delegate;

      TypeToken<SubBar<T>> fieldTypeAsSubBar() {
        return new TypeToken<SubBar<T>>() {};
      }
    }

    Field delegateField = SubBar.class.getDeclaredField("delegate");
    // barType is Bar<T>, a ParameterizedType with no generic arguments specified

    peer.play()

    // Play it back.
    val connection = connect(peer)
    val stream = connection.newStream(headerEntries("a", "android"), true)
    stream.enqueueTrailers(headersOf("foo", "bar"))
    val sink = stream.sink.buffer()
    sink.writeUtf8("abcdefghi")
    sink.close()

    // Verify the peer received what was expected.
    val headers1 = peer.takeFrame()