.isEqualTo("a"b<c>d&e"f'");
    // Test '\t', '\n' and '\r' are escaped.
    assertThat(xmlAttributeEscaper.escape("a\tb\nc\rd")).isEqualTo("a	b
c
d");
  }

  // Helper to assert common properties of xml escapers.
  static void assertBasicXmlEscaper(
      CharEscaper xmlEscaper, boolean shouldEscapeQuotes, boolean shouldEscapeWhitespaceChars) {

        .isEqualTo("a"b<c>d&e"f'");
    // Test '\t', '\n' and '\r' are escaped.
    assertThat(xmlAttributeEscaper.escape("a\tb\nc\rd")).isEqualTo("a	b
c
d");
  }

  // Helper to assert common properties of xml escapers.
  static void assertBasicXmlEscaper(
      CharEscaper xmlEscaper, boolean shouldEscapeQuotes, boolean shouldEscapeWhitespaceChars) {

'\x07'
'\xff'
'\u12e4'
'\U00101234'
'\''         // rune literal containing single quote character
'aa'         // illegal: too many characters
'\k'         // illegal: k is not recognized after a backslash
'\xa'        // illegal: too few hexadecimal digits
'\0'         // illegal: too few octal digits
'\400'       // illegal: octal value over 255
'\uDFFF'     // illegal: surrogate half