2 files changed, 31 insertions, 1 deletions
diff --git a/bs4/element.py b/bs4/element.py
index 282193e..c1ad992 100644
--- a/bs4/element.py
+++ b/bs4/element.py
@@ -677,6 +677,12 @@ class CData(NavigableString):
     PREFIX = u'<![CDATA['
     SUFFIX = u']]>'
 
+    def output_ready(self, formatter="minimal"):
+        """CData strings are passed into the formatter.
+        But the return value is ignored."""
+        self.format_string(self, formatter)
+        return self.PREFIX + self + self.SUFFIX
+
 
 class ProcessingInstruction(NavigableString):
 
@@ -791,7 +797,7 @@ class Tag(PageElement):
     @string.setter
     def string(self, string):
         self.clear()
-        self.append(unicode(string))
+        self.append(string.__class__(string))
 
     def _all_strings(self, strip=False):
         """Yield all child strings, possibly stripping them."""
diff --git a/bs4/tests/test_tree.py b/bs4/tests/test_tree.py
index 5acaeea..2dea886 100644
--- a/bs4/tests/test_tree.py
+++ b/bs4/tests/test_tree.py
@@ -995,6 +995,12 @@ class TestTreeModification(SoupTest):
         soup.b.string = soup.c.string
         self.assertEqual(soup.a.encode(), b"<a><b>bar</b><c>bar</c></a>")
 
+    def test_set_string_preserves_class_of_string(self):
+        soup = self.soup("<a></a>")
+        cdata = CData("foo")
+        soup.a.string = cdata
+        self.assertTrue(isinstance(soup.a.string, CData))
+
 class TestElementObjects(SoupTest):
     """Test various features of element objects."""
 
@@ -1346,6 +1352,24 @@ class TestNavigableStringSubclasses(SoupTest):
         self.assertEqual(soup.find(text="foo"), "foo")
         self.assertEqual(soup.contents[0], "foo")
 
+    def test_cdata_is_never_formatted(self):
+        """Text inside a CData object is passed into the formatter.
+
+        But the return value is ignored.
+        """
+
+        self.count = 0
+        def increment(*args):
+            self.count += 1
+            return "BITTER FAILURE"
+
+        soup = self.soup("")
+        cdata = CData("<><><>")
+        soup.insert(1, cdata)
+        self.assertEqual(
+            b"<![CDATA[<><><>]]>", soup.encode(formatter=increment))
+        self.assertEqual(1, self.count)
+
     def test_doctype_ends_in_newline(self):
         # Unlike other NavigableString subclasses, a DOCTYPE always ends
         # in a newline.