Add test for setting Radio Buttons

The test file has 4 radio buttons in a group on page 0. We set on every one of them and check that the other three are set to Off.
Finally confirm that setting off all buttons also sets the group value to Off.

tests/test_widgets.py

@@ -7,6 +7,7 @@
 
 scriptdir = os.path.abspath(os.path.dirname(__file__))
 filename = os.path.join(scriptdir, "resources", "widgettest.pdf")
+file_2333 = os.path.join(scriptdir, "resources", "test-2333.pdf")
 
 
 doc = fitz.open()
@@ -158,6 +159,32 @@ def test_text2():
     assert field.field_type_string == "Text"
 
 
+def test_2333():
+    doc = fitz.open(file_2333)
+    page = doc[0]
+
+    def values():
+        return set(
+            (
+                doc.xref_get_key(635, "AS")[1],
+                doc.xref_get_key(636, "AS")[1],
+                doc.xref_get_key(637, "AS")[1],
+                doc.xref_get_key(638, "AS")[1],
+                doc.xref_get_key(127, "V")[1],
+            )
+        )
+
+    for i, xref in enumerate((635, 636, 637, 638)):
+        w = page.load_widget(xref)
+        w.field_value = True
+        w.update()
+        assert values() == set(("/Off", f"{i}", f"/{i}"))
+    w.field_value=False
+    w.update()
+    assert values() == set(("Off", "/Off"))
+
+
+
 # def test_deletewidget():
 #     pdf = fitz.open(filename)
 #     page = pdf[0]