Rewrote form widget tests as proper unittests.

This is preparation for landing the template-based widget rendering
patch and goes a long way to making these tests more useful for future
development. The old doctest heritage is strong here.

tests/forms_tests/widget_tests/test_textarea.py

@@ -0,0 +1,34 @@
+from django.forms import Textarea
+from django.utils.safestring import mark_safe
+
+from .base import WidgetTest
+
+
+class TextareaTest(WidgetTest):
+    widget = Textarea()
+
+    def test_render(self):
+        self.check_html(self.widget, 'msg', 'value', html=(
+            '<textarea rows="10" cols="40" name="msg">value</textarea>'
+        ))
+
+    def test_render_required(self):
+        widget = Textarea()
+        widget.is_required = True
+        self.check_html(widget, 'msg', 'value', html='<textarea rows="10" cols="40" name="msg">value</textarea>')
+
+    def test_render_empty(self):
+        self.check_html(self.widget, 'msg', '', html='<textarea rows="10" cols="40" name="msg"></textarea>')
+
+    def test_render_none(self):
+        self.check_html(self.widget, 'msg', None, html='<textarea rows="10" cols="40" name="msg"></textarea>')
+
+    def test_escaping(self):
+        self.check_html(self.widget, 'msg', 'some "quoted" & ampersanded value', html=(
+            '<textarea rows="10" cols="40" name="msg">some &quot;quoted&quot; &amp; ampersanded value</textarea>'
+        ))
+
+    def test_mark_safe(self):
+        self.check_html(self.widget, 'msg', mark_safe('pre &quot;quoted&quot; value'), html=(
+            '<textarea rows="10" cols="40" name="msg">pre &quot;quoted&quot; value</textarea>'
+        ))