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_checkboxselectmultiple.py

@@ -0,0 +1,115 @@
+from django.forms import CheckboxSelectMultiple
+
+from .base import WidgetTest
+
+
+class CheckboxSelectMultipleTest(WidgetTest):
+    widget = CheckboxSelectMultiple()
+
+    def test_render_value(self):
+        self.check_html(self.widget, 'beatles', ['J'], choices=self.beatles, html=(
+            """<ul>
+            <li><label><input checked="checked" type="checkbox" name="beatles" value="J" /> John</label></li>
+            <li><label><input type="checkbox" name="beatles" value="P" /> Paul</label></li>
+            <li><label><input type="checkbox" name="beatles" value="G" /> George</label></li>
+            <li><label><input type="checkbox" name="beatles" value="R" /> Ringo</label></li>
+            </ul>"""
+        ))
+
+    def test_render_value_multiple(self):
+        self.check_html(self.widget, 'beatles', ['J', 'P'], choices=self.beatles, html=(
+            """<ul>
+            <li><label><input checked="checked" type="checkbox" name="beatles" value="J" /> John</label></li>
+            <li><label><input checked="checked" type="checkbox" name="beatles" value="P" /> Paul</label></li>
+            <li><label><input type="checkbox" name="beatles" value="G" /> George</label></li>
+            <li><label><input type="checkbox" name="beatles" value="R" /> Ringo</label></li>
+            </ul>"""
+        ))
+
+    def test_render_none(self):
+        """
+        If the value is None, none of the options are selected.
+        """
+        self.check_html(self.widget, 'beatles', None, choices=self.beatles, html=(
+            """<ul>
+            <li><label><input type="checkbox" name="beatles" value="J" /> John</label></li>
+            <li><label><input type="checkbox" name="beatles" value="P" /> Paul</label></li>
+            <li><label><input type="checkbox" name="beatles" value="G" /> George</label></li>
+            <li><label><input type="checkbox" name="beatles" value="R" /> Ringo</label></li>
+            </ul>"""
+        ))
+
+    def test_nested_choices(self):
+        nested_choices = (
+            ('unknown', 'Unknown'),
+            ('Audio', (('vinyl', 'Vinyl'), ('cd', 'CD'))),
+            ('Video', (('vhs', 'VHS'), ('dvd', 'DVD'))),
+        )
+        html = """
+        <ul id="media">
+        <li>
+        <label for="media_0"><input id="media_0" name="nestchoice" type="checkbox" value="unknown" /> Unknown</label>
+        </li>
+        <li>Audio<ul id="media_1">
+        <li>
+        <label for="media_1_0">
+        <input checked="checked" id="media_1_0" name="nestchoice" type="checkbox" value="vinyl" /> Vinyl
+        </label>
+        </li>
+        <li>
+        <label for="media_1_1"><input id="media_1_1" name="nestchoice" type="checkbox" value="cd" /> CD</label>
+        </li>
+        </ul></li>
+        <li>Video<ul id="media_2">
+        <li>
+        <label for="media_2_0"><input id="media_2_0" name="nestchoice" type="checkbox" value="vhs" /> VHS</label>
+        </li>
+        <li>
+        <label for="media_2_1">
+        <input checked="checked" id="media_2_1" name="nestchoice" type="checkbox" value="dvd" /> DVD
+        </label>
+        </li>
+        </ul></li>
+        </ul>
+        """
+        self.check_html(
+            self.widget, 'nestchoice', ('vinyl', 'dvd'),
+            choices=nested_choices, attrs={'id': 'media'}, html=html,
+        )
+
+    def test_separate_ids(self):
+        """
+        Each input gets a separate ID.
+        """
+        choices = [('a', 'A'), ('b', 'B'), ('c', 'C')]
+        html = """
+        <ul id="abc">
+        <li>
+        <label for="abc_0"><input checked="checked" type="checkbox" name="letters" value="a" id="abc_0" /> A</label>
+        </li>
+        <li><label for="abc_1"><input type="checkbox" name="letters" value="b" id="abc_1" /> B</label></li>
+        <li>
+        <label for="abc_2"><input checked="checked" type="checkbox" name="letters" value="c" id="abc_2" /> C</label>
+        </li>
+        </ul>
+        """
+        self.check_html(self.widget, 'letters', ['a', 'c'], choices=choices, attrs={'id': 'abc'}, html=html)
+
+    def test_separate_ids_constructor(self):
+        """
+        Each input gets a separate ID when the ID is passed to the constructor.
+        """
+        widget = CheckboxSelectMultiple(attrs={'id': 'abc'})
+        choices = [('a', 'A'), ('b', 'B'), ('c', 'C')]
+        html = """
+        <ul id="abc">
+        <li>
+        <label for="abc_0"><input checked="checked" type="checkbox" name="letters" value="a" id="abc_0" /> A</label>
+        </li>
+        <li><label for="abc_1"><input type="checkbox" name="letters" value="b" id="abc_1" /> B</label></li>
+        <li>
+        <label for="abc_2"><input checked="checked" type="checkbox" name="letters" value="c" id="abc_2" /> C</label>
+        </li>
+        </ul>
+        """
+        self.check_html(widget, 'letters', ['a', 'c'], choices=choices, html=html)