diff -r 000000000000 -r 6474c204b198 js/src/jsapi-tests/testUTF8.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jsapi-tests/testUTF8.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "jsapi.h"
+#include "jsstr.h"
+
+#include "js/CharacterEncoding.h"
+#include "jsapi-tests/tests.h"
+
+BEGIN_TEST(testUTF8_badUTF8)
+{
+    static const char badUTF8[] = "...\xC0...";
+    JSString *str = JS_NewStringCopyZ(cx, badUTF8);
+    CHECK(str);
+    const jschar *chars = JS_GetStringCharsZ(cx, str);
+    CHECK(chars);
+    CHECK(chars[3] == 0x00C0);
+    return true;
+}
+END_TEST(testUTF8_badUTF8)
+
+BEGIN_TEST(testUTF8_bigUTF8)
+{
+    static const char bigUTF8[] = "...\xFB\xBF\xBF\xBF\xBF...";
+    JSString *str = JS_NewStringCopyZ(cx, bigUTF8);
+    CHECK(str);
+    const jschar *chars = JS_GetStringCharsZ(cx, str);
+    CHECK(chars);
+    CHECK(chars[3] == 0x00FB);
+    return true;
+}
+END_TEST(testUTF8_bigUTF8)
+
+BEGIN_TEST(testUTF8_badSurrogate)
+{
+    static const jschar badSurrogate[] = { 'A', 'B', 'C', 0xDEEE, 'D', 'E', 0 };
+    JS::TwoByteChars tbchars(badSurrogate, js_strlen(badSurrogate));
+    JS::Latin1CharsZ latin1 = JS::LossyTwoByteCharsToNewLatin1CharsZ(cx, tbchars);
+    CHECK(latin1);
+    CHECK(latin1[3] == 0x00EE);
+    return true;
+}
+END_TEST(testUTF8_badSurrogate)