assertEquals("<hello><hi><lo>", charEscaper.escape("x\uD800\uDC00"));
    assertEquals("<hello><hi><lo>", unicodeEscaper.escape("x\uD800\uDC00"));

    // Test that wrapped escapers acquire good Unicode semantics.
    assertEquals("<hi><hello><lo>", charEscaper.escape("\uD800x\uDC00"));
    try {
      unicodeEscaper.escape("\uD800x\uDC00");
      fail("should have failed for bad Unicode input");

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  // Helper to assert common expected behaviour of uri escapers.

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    // simple string tests
    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {

    assertEquals("<tab>Fish <and> Chips<newline>", escaper.escape("\tFish & Chips\n"));

    // Verify that everything else is left unescaped.
    String safeChars = "\0\u0100\uD800\uDC00\uFFFF";
    assertEquals(safeChars, escaper.escape(safeChars));

    // Ensure that Unicode escapers behave correctly wrt badly formed input.
    String badUnicode = "\uDC00\uD800";
    try {
      escaper.escape(badUnicode);
      fail("should fail for bad Unicode");

    assertEquals("<hello><hi><lo>", charEscaper.escape("x\uD800\uDC00"));
    assertEquals("<hello><hi><lo>", unicodeEscaper.escape("x\uD800\uDC00"));

    // Test that wrapped escapers acquire good Unicode semantics.
    assertEquals("<hi><hello><lo>", charEscaper.escape("\uD800x\uDC00"));
    try {
      unicodeEscaper.escape("\uD800x\uDC00");
      fail("should have failed for bad Unicode input");

import static org.junit.Assert.assertThat;

import org.junit.Test;

/**
 * @author shinsuke
 *
 */
public class JsonUtilTest {
    @Test
    public void escape() {
        assertThat(JsonUtil.escape("abc123あア亜"), is("abc123あア亜"));
        assertThat(JsonUtil.escape("\\\"/\b\t\n\f\r\0"), is("\\\\\\\"\\/\\b\\t\\n\\f\\r\\u0000"));
    }

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  // Helper to assert common expected behaviour of uri escapers.

    assertEquals("xxx", htmlEscaper().escape("xxx"));
    assertEquals(""test"", htmlEscaper().escape("\"test\""));
    assertEquals("'test'", htmlEscaper().escape("\'test'"));
    assertEquals("test & test & test", htmlEscaper().escape("test & test & test"));
    assertEquals("test &lt;&lt; 1", htmlEscaper().escape("test << 1"));
    assertEquals("test &gt;&gt; 1", htmlEscaper().escape("test >> 1"));

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    // simple string tests
    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {

 * individual {@code char} values, it is not safe to assume that {@code escape(s)} is equivalent to
 * {@code escape(s.substring(0, n)) + escape(s.substring(n))} for arbitrary {@code n}. This is
 * because of the possibility of splitting a surrogate pair. The only case in which it is safe to
 * escape strings and concatenate the results is if you can rule out this possibility, either by