assertEquals("", Strings.commonSuffix("xyz", "abcde"));
    assertEquals("", Strings.commonSuffix("xyz", "xyzabc"));
    assertEquals("c", Strings.commonSuffix("abc", "ccccc"));
    assertEquals("aa", Strings.commonSuffix("aa", "aaaaa"));
    assertEquals("abc", Strings.commonSuffix(new StringBuilder("xyzabc"), "xxxabc"));

    // Identical valid surrogate pairs.
    assertEquals(

    assertEquals("", Strings.commonSuffix("xyz", "abcde"));
    assertEquals("", Strings.commonSuffix("xyz", "xyzabc"));
    assertEquals("c", Strings.commonSuffix("abc", "ccccc"));
    assertEquals("aa", Strings.commonSuffix("aa", "aaaaa"));
    assertEquals("abc", Strings.commonSuffix(new StringBuilder("xyzabc"), "xxxabc"));

    // Identical valid surrogate pairs.
    assertEquals(

		tests: []testFnc{
			testRead{100, "\x00abc\x00\x00", errMissData},
		},
	}, {
		maker: makeSparse{makeReg{"abc", 8}, sparseDatas{{1, 3}, {6, 5}}, 15},
		tests: []testFnc{
			testRead{100, "\x00abc\x00\x00", io.ErrUnexpectedEOF},
		},
	}, {
		maker: makeSparse{makeReg{"abcde", 5}, sparseDatas{{1, 3}, {6, 5}}, 15},
		tests: []testFnc{
			testRead{100, "\x00abc\x00\x00de", errMissData},
		},
	}, {

			testRemaining{5, 5},
			testWrite{"abc", 3, nil},
			testRemaining{2, 2},
			testReadFrom{fileOps{"\x00\x00"}, 2, nil},
			testRemaining{0, 0},
		},
	}, {
		maker: makeReg{5, "\x00\x00abc"},
		tests: []testFnc{
			testRemaining{5, 5},
			testWrite{"\x00\x00", 2, nil},
			testRemaining{3, 3},
			testWrite{"abc", 3, nil},
			testReadFrom{fileOps{"z"}, 0, ErrWriteTooLong},

		}
	}
}

var scanTests = []string{
	"",
	"a",
	"¼",
	"☹",
	"\x81",   // UTF-8 error
	"\uFFFD", // correctly encoded RuneError
	"abcdefgh",
	"abc def\n\t\tgh    ",
	"abc¼☹\x81\uFFFD日本語\x82abc",
}

func TestScanByte(t *testing.T) {
	for n, test := range scanTests {
		buf := strings.NewReader(test)
		s := NewScanner(buf)
		s.Split(ScanBytes)
		var i int
		for i = 0; s.Scan(); i++ {