5 files changed, 33 insertions, 8 deletions
diff --git a/bs4/tests/test_html5lib.py b/bs4/tests/test_html5lib.py
index 3a04787..371463a 100644
--- a/bs4/tests/test_html5lib.py
+++ b/bs4/tests/test_html5lib.py
@@ -22,7 +22,7 @@ class HTML5LibBuilderSmokeTest(SoupTest, HTML5TreeBuilderSmokeTest):
 
     @property
     def default_builder(self):
-        return HTML5TreeBuilder()
+        return HTML5TreeBuilder
 
     def test_soupstrainer(self):
         # The html5lib tree builder does not support SoupStrainers.
diff --git a/bs4/tests/test_htmlparser.py b/bs4/tests/test_htmlparser.py
index 0381c7d..790489a 100644
--- a/bs4/tests/test_htmlparser.py
+++ b/bs4/tests/test_htmlparser.py
@@ -9,9 +9,7 @@ from bs4.builder._htmlparser import BeautifulSoupHTMLParser
 
 class HTMLParserTreeBuilderSmokeTest(SoupTest, HTMLTreeBuilderSmokeTest):
 
-    @property
-    def default_builder(self):
-        return HTMLParserTreeBuilder()
+    default_builder = HTMLParserTreeBuilder
 
     def test_namespaced_system_doctype(self):
         # html.parser can't handle namespaced doctypes, so skip this one.
diff --git a/bs4/tests/test_lxml.py b/bs4/tests/test_lxml.py
index 1a4f27c..3b7858f 100644
--- a/bs4/tests/test_lxml.py
+++ b/bs4/tests/test_lxml.py
@@ -36,7 +36,7 @@ class LXMLTreeBuilderSmokeTest(SoupTest, HTMLTreeBuilderSmokeTest):
 
     @property
     def default_builder(self):
-        return LXMLTreeBuilder()
+        return LXMLTreeBuilder
 
     def test_out_of_range_entity(self):
         self.assertSoupEquals(
@@ -79,7 +79,7 @@ class LXMLXMLTreeBuilderSmokeTest(SoupTest, XMLTreeBuilderSmokeTest):
 
     @property
     def default_builder(self):
-        return LXMLTreeBuilderForXML()
+        return LXMLTreeBuilderForXML
 
     def test_namespace_indexing(self):
         # We should not track un-prefixed namespaces as we can only hold one
diff --git a/bs4/tests/test_soup.py b/bs4/tests/test_soup.py
index 1c6b7a6..213255d 100644
--- a/bs4/tests/test_soup.py
+++ b/bs4/tests/test_soup.py
@@ -24,6 +24,7 @@ from bs4.dammit import (
     EncodingDetector,
 )
 from bs4.testing import (
+    default_builder,
     SoupTest,
     skipIf,
 )
@@ -89,7 +90,33 @@ class TestConstructor(SoupTest):
         self.assertEqual(builder, soup.builder)
         self.assertEqual(kwargs, builder.called_with)
 
-
+    def test_cdata_list_attributes(self):
+        # Most attribute values are represented as scalars, but the
+        # HTML standard says that some attributes, like 'class' have
+        # space-separated lists as values.
+        markup = '<a id=" an id " class=" a class "></a>'
+        soup = self.soup(markup)
+
+        # Note that the spaces are stripped for 'class' but not for 'id'.
+        a = soup.a
+        self.assertEqual(" an id ", a['id'])
+        self.assertEqual(["a", "class"], a['class'])
+
+        # TreeBuilder takes an argument called 'cdata_list_attributes'  which lets
+        # you customize or disable this. As always, you can customize the TreeBuilder
+        # by passing in a keyword argument to the BeautifulSoup constructor.
+        soup = self.soup(markup, builder=default_builder, cdata_list_attributes=None)
+        self.assertEqual(" a class ", soup.a['class'])
+
+        # Here are two ways of saying that `id` is a CDATA list
+        # attribute and 'class' is not.
+        for switcheroo in ({'*': 'id'}, {'a': 'id'}):
+            soup = self.soup(markup, builder=None, cdata_list_attributes=switcheroo)
+            a = soup.a
+            self.assertEqual(["an", "id"], a['id'])
+            self.assertEqual(" a class ", a['class'])
+
+        
 class TestWarnings(SoupTest):
 
     def _no_parser_specified(self, s, is_there=True):
diff --git a/bs4/tests/test_tree.py b/bs4/tests/test_tree.py
index 6d79454..a14928e 100644
--- a/bs4/tests/test_tree.py
+++ b/bs4/tests/test_tree.py
@@ -896,7 +896,7 @@ class TestTreeModification(SoupTest):
         self.assertEqual(soup.a.contents[0].next_element, "bar")
 
     def test_insert_tag(self):
-        builder = self.default_builder
+        builder = self.default_builder()
         soup = self.soup(
             "<a><b>Find</b><c>lady!</c><d></d></a>", builder=builder)
         magic_tag = Tag(soup, builder, 'magictag')