+ "abcdefghijklmnopqrstuvwxyz"
            + "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
            + "1234567890";
    assertEquals(s, xmlEscaper.escape(s));

    // Test ASCII control characters.
    for (char ch = 0; ch < 0x20; ch++) {
      if (ch == '\t' || ch == '\n' || ch == '\r') {
        // Only these whitespace chars are permitted in XML,
        if (shouldEscapeWhitespaceChars) {

      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  @GwtIncompatible // Chars.fromByteArray
  public void testFromByteArray() {
    assertThat(Chars.fromByteArray(new byte[] {0x23, 0x45, (byte) 0xDC})).isEqualTo('\u2345');
    assertThat(Chars.fromByteArray(new byte[] {(byte) 0xFE, (byte) 0xDC})).isEqualTo('\uFEDC');
  }

  @GwtIncompatible // Chars.fromByteArray

    assertThat(Shorts.toByteArray((short) 0x2345)).isEqualTo(new byte[] {0x23, 0x45});
    assertThat(Shorts.toByteArray((short) 0xFEDC)).isEqualTo(new byte[] {(byte) 0xFE, (byte) 0xDC});
  }

  @GwtIncompatible // Shorts.fromByteArray
  public void testFromByteArray() {
    assertThat(Shorts.fromByteArray(new byte[] {0x23, 0x45})).isEqualTo((short) 0x2345);

      // TODO(cpovirk): Use SourceCodeEscapers if it is added to Guava.
      StringBuilder escapedInput = new StringBuilder();
      for (char c : input.toCharArray()) {
        if (c >= 0x20 && c <= 0x7E) {
          escapedInput.append(c);
        } else {
          escapedInput.append(String.format("\\u%04x", (int) c));
        }
      }