assertThat(stringPrep("\uf8ff")).isNull()
    assertThat(stringPrep("\udbff\udffd")).isNull() // Note that this is one code point.
  }

  @Test fun prohibitionNonCharacter() {
    assertThat(stringPrep("\ufdd0")).isNull()
    assertThat(stringPrep("\ufffe")).isNull()
    assertThat(stringPrep("\udbff\udffe")).isNull()
  }

  /**
   * Because our API always transcodes through UTF-8, and that transcoding replaces unpaired

    assertThat("https://co.uk".toHttpUrl().topPrivateDomain()).isNull()
    assertThat("https://square".toHttpUrl().topPrivateDomain()).isNull()
    assertThat("https://栃木.jp".toHttpUrl().topPrivateDomain()).isNull()
    assertThat("https://xn--4pvxs.jp".toHttpUrl().topPrivateDomain()).isNull()
    assertThat("https://localhost".toHttpUrl().topPrivateDomain()).isNull()
    assertThat("https://127.0.0.1".toHttpUrl().topPrivateDomain()).isNull()

        .url("https://square.com")
        .build()
    assertThat(request.tag<Any>()).isNull()
    assertThat(request.tag(Any::class)).isNull()
    assertThat(request.tag(String::class)).isNull()

    // Alternate access APIs also work.
    assertThat(request.tag<String>()).isNull()
    assertThat(request.tag(String::class)).isNull()
  }

  @Test
  fun defaultTag() {
    val tag = "1234"
    val request =

    CompactLinkedHashMap<Integer, String> map = CompactLinkedHashMap.create();
    assertThat(map.needsAllocArrays()).isTrue();
    assertThat(map.entries).isNull();
    assertThat(map.keys).isNull();
    assertThat(map.values).isNull();
    assertThat(map.links).isNull();

    map.put(1, Integer.toString(1));
    assertThat(map.needsAllocArrays()).isFalse();
    assertThat(map.entries).hasLength(CompactHashing.DEFAULT_SIZE);

    assertThat(publicSuffixDatabase.getEffectiveTldPlusOne("aaa")).isNull()
    assertThat(publicSuffixDatabase.getEffectiveTldPlusOne("ggg")).isNull()
    assertThat(publicSuffixDatabase.getEffectiveTldPlusOne("ccc")).isNull()
    assertThat(publicSuffixDatabase.getEffectiveTldPlusOne("eee")).isNull()
  }

  @Test fun exceptionRule() {
    val exception =
      Buffer()

  fun assertNoNetworkResponse() =
    apply {
      assertThat(response!!.networkResponse).isNull()
    }

  /** Asserts that the current response didn't use the cache.  */
  fun assertNoCacheResponse() =
    apply {
      assertThat(response!!.cacheResponse).isNull()
    }

  /**
   * Asserts that the current response used the cache and returns the cache response.
   */

    assertThat(graph.removeEdge(1, 2)).isEqualTo("valueA");
    assertThat(graph.removeEdge(1, 2)).isNull();
    assertThat(graph.removeEdge(2, 1)).isEqualTo("valueB");
    assertThat(graph.removeEdge(2, 1)).isNull();
    assertThat(graph.removeEdge(2, 3)).isEqualTo("valueC");
    assertThat(graph.removeEdge(2, 3)).isNull();
  }

  @Test
  public void removeEdge_undirected() {

    assertThat(parse(url, "a\u0000b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0000d")).isNull()
    assertThat(parse(url, "a\u0001b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0001d")).isNull()
    assertThat(parse(url, "a\u0009b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0009d")).isNull()
    assertThat(parse(url, "a\u001fb=cd")).isNull()
    assertThat(parse(url, "ab=c\u001fd")).isNull()

    assertThat(Ints.tryParse("")).isNull();
    assertThat(Ints.tryParse("-")).isNull();
    assertThat(Ints.tryParse("+1")).isNull();
    assertThat(Ints.tryParse("9999999999999999")).isNull();
    assertWithMessage("Max integer + 1")
        .that(Ints.tryParse(Long.toString(((long) GREATEST) + 1)))
        .isNull();
    assertWithMessage("Max integer * 10")

    taskFaker.runNextTask()

    // Don't allow edits under any circumstances.
    assertThat(cache.edit("a")).isNull()
    assertThat(cache.edit("c")).isNull()
    cache["a"]!!.use {
      assertThat(it.edit()).isNull()
    }
  }

  @ParameterizedTest
  @ArgumentsSource(FileSystemParamProvider::class)