CountingLoader countingLoader = new CountingLoader();
    LoadingCache<Object, Object> cache =
        CacheBuilder.newBuilder().concurrencyLevel(1).weakKeys().build(countingLoader);

    Object key = new Object();
    assertThat(cache.getUnchecked(key)).isNotNull();
    assertThat(cache.size()).isEqualTo(1);

    CacheTesting.simulateKeyReclamation(cache, key);

  }

  @Test fun specialKInHostname() {
    // https://github.com/apache/httpcomponents-client/commit/303e435d7949652ea77a6c50df1c548682476b6e
    // https://www.gosecure.net/blog/2020/10/27/weakness-in-java-tls-host-verification/
    val heldCertificate =
      HeldCertificate
        .Builder()
        .commonName("Foo Corp")
        .addSubjectAlternativeName("k.com")

    assertInvalid("http://.a/", "Invalid URL host: \".a\"")
    assertInvalid("http://../", "Invalid URL host: \"..\"")
  }

  @Test
  fun hostnameTelephone() {
    // https://www.gosecure.net/blog/2020/10/27/weakness-in-java-tls-host-verification/

    // Map the single character telephone symbol (℡) to the string "tel".
    assertThat(parse("http://\u2121").host).isEqualTo("tel")