@CollectionSize.Require(ONE)
  @CollectionFeature.Require(absent = NON_STANDARD_TOSTRING)
  public void testToString_size1() {
    assertEquals(
        "size1Collection.toString should return [{element}]",
        "[" + e0() + "]",
        collection.toString());
  }

  @CollectionSize.Require(SEVERAL)
  @CollectionFeature.Require(value = KNOWN_ORDER, absent = NON_STANDARD_TOSTRING)
  public void testToString_sizeSeveral() {

  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemove_supportedPresent() {
    assertTrue(getMap().remove(k0(), v0()));
    expectMissing(e0());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_supportedPresentKeyWrongValue() {
    assertFalse(getMap().remove(k0(), v3()));
    expectUnchanged();
  }

  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemove_supportedPresent() {
    assertTrue(getMap().remove(k0(), v0()));
    expectMissing(e0());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_supportedPresentKeyWrongValue() {
    assertFalse(getMap().remove(k0(), v3()));
    expectUnchanged();
  }

    assertEscaping(e, "%7F", '\u007f'); // del
    assertEscaping(e, "%C2%80", '\u0080'); // xx-00010,x-000000
    assertEscaping(e, "%DF%BF", '\u07ff'); // xx-11111,x-111111
    assertEscaping(e, "%E0%A0%80", '\u0800'); // xxx-0000,x-100000,x-00,0000
    assertEscaping(e, "%EF%BF%BF", '\uffff'); // xxx-1111,x-111111,x-11,1111
    assertUnicodeEscaping(e, "%F0%90%80%80", '\uD800', '\uDC00');

    assertEscaping(e, "%7F", '\u007f'); // del
    assertEscaping(e, "%C2%80", '\u0080'); // xx-00010,x-000000
    assertEscaping(e, "%DF%BF", '\u07ff'); // xx-11111,x-111111
    assertEscaping(e, "%E0%A0%80", '\u0800'); // xxx-0000,x-100000,x-00,0000
    assertEscaping(e, "%EF%BF%BF", '\uffff'); // xxx-1111,x-111111,x-11,1111
    assertUnicodeEscaping(e, "%F0%90%80%80", '\uD800', '\uDC00');

                k0(),
                (k, v) -> {
                  assertEquals(k0(), k);
                  assertEquals(v0(), v);
                  return null;
                }));
    expectMissing(e0());
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  @CollectionSize.Require(absent = ZERO)
  public void testComputeIfPresent_nullTreatedAsAbsent() {
    initMapWithNullValue();
    assertNull(

    assertEquals("remove(present) should return the associated value", v0(), getMap().remove(k0()));
    assertEquals(
        "remove(present) should decrease a map's size by one.", initialSize - 1, getMap().size());
    expectMissing(e0());
  }

  @MapFeature.Require({FAILS_FAST_ON_CONCURRENT_MODIFICATION, SUPPORTS_REMOVE})
  @CollectionSize.Require(SEVERAL)
  public void testRemovePresentConcurrentWithEntrySetIteration() {
    assertThrows(

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_unsupportedPresent() {
    try {
      assertFalse("add(present) should return false or throw", collection.add(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @CollectionFeature.Require(
      value = {SUPPORTS_ADD, ALLOWS_NULL_VALUES},
      absent = RESTRICTS_ELEMENTS)

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_unsupportedPresent() {
    try {
      assertFalse("add(present) should return false or throw", collection.add(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @CollectionFeature.Require(
      value = {SUPPORTS_ADD, ALLOWS_NULL_VALUES},
      absent = RESTRICTS_ELEMENTS)

                v3(),
                (oldV, newV) -> {
                  assertEquals(v0(), oldV);
                  assertEquals(v3(), newV);
                  return null;
                }));
    expectMissing(e0());
  }

  public void testMergeNullValue() {
    try {
      getMap()
          .merge(
              k0(),
              null,
              (oldV, newV) -> {