Added a test for the scrollspy component that ensures the active class is applied on scroll

Author: codytodonnell

tests/scrollspy_test.py

@@ -0,0 +1,42 @@
+import dash
+import dash_html_components as html
+import dash_mp_components
+
+"""
+Tests the basic scrollspy functionality
+Ensures first link is active initially
+Ensures second link is active after its item is scrolled to
+"""
+def test_scrollspy_menu(dash_duo):
+    app = dash.Dash(__name__)
+    app.layout = html.Div(className='scrollspy', children=[
+      dash_mp_components.Scrollspy(
+        menuGroups=[{'label': 'Table of Contents', 'items': [{'label': 'One', 'targetId': 'one'}, {'label': 'Two', 'targetId': 'two'}, {'label': 'Three', 'targetId': 'three'}]}],
+        menuClassName="menu",
+        menuItemContainerClassName="menu-list",
+        activeClassName="is-active",
+        offset=0
+      ),
+      html.Div(className='content', children=[
+          html.Div(id='one', style={'height': '600px'}, children=[
+              html.H1('One'),
+              html.P('lorem ipsum'),
+          ]),
+          html.Div(id='two', style={'height': '600px'}, children=[
+              html.H1('Two'),
+              html.P('lorem ipsum'),
+          ]),
+          html.Div(id='three', style={'height': '600px'}, children=[
+              html.H1('Three'),
+              html.P('lorem ipsum'),
+          ]),
+      ])
+    ])
+    dash_duo.start_server(app)
+    dash_duo.driver.set_window_size(1920, 1080)
+    links = dash_duo.find_elements('a')
+    assert links[0].text == 'One'
+    assert links[0].get_attribute('class') == 'is-active'
+    second_block = dash_duo.find_element('#two')
+    dash_duo.driver.execute_script("arguments[0].scrollIntoView();", second_block)
+    assert links[1].get_attribute('class') == 'is-active'