Explicitly test setting options traitlet

Author: pbugnion

ipywidgets/widgets/tests/test_widget_selection.py

@@ -20,6 +20,26 @@ def test_raise_mapping_options(self):
         with pytest.raises(TypeError):
             Dropdown(options={'One': 1, 'Two': 2, 'Three': 3})
 
+    def test_setting_options_from_list(self):
+        d = Dropdown()
+        assert d.options == ()
+        d.options = ['One', 'Two', 'Three']
+        assert d.get_state('_options_labels') == {'_options_labels': ('One', 'Two', 'Three')}
+
+    def test_setting_options_from_list_tuples(self):
+        d = Dropdown()
+        assert d.options == ()
+        d.options = [('One', 1), ('Two', 2), ('Three', 3)]
+        assert d.get_state('_options_labels') == {'_options_labels': ('One', 'Two', 'Three')}
+        d.value = 2
+        assert d.get_state('index') == {'index': 1}
+
+    def test_setting_options_from_dict(self):
+        d = Dropdown()
+        assert d.options == ()
+        with pytest.raises(TypeError):
+            d.options = {'One': 1}
+
 
 class TestSelectionSlider(TestCase):