change test and tweak code

Author: almarklein

src/fragments/Slider.react.js

@@ -17,9 +17,7 @@ export default class Slider extends Component {
             ? createSliderWithTooltip(ReactSlider)
             : ReactSlider;
         this._computeStyle = computeSliderStyle();
-        this.state = {
-            value: props.value
-        };
+        this.state = {value: props.value};
     }
 
     UNSAFE_componentWillReceiveProps(newProps) {
@@ -35,8 +33,10 @@ export default class Slider extends Component {
     }
 
     UNSAFE_componentWillMount() {
-        this.props.setProps({drag_value: this.props.value});
-        this.setState({value: this.props.value});
+        if (this.props.value !== null) {
+            this.props.setProps({drag_value: this.props.value});
+            this.setState({value: this.props.value});
+        }
     }
 
     render() {

tests/integration/sliders/test_sliders.py

@@ -189,7 +189,8 @@ def update_output(value):
 
     dash_dcc.start_server(app)
     dash_dcc.wait_for_text_to_equal("#out-value", "You have selected 5")
-    assert dash_dcc.find_element("#out-drag-value").text == "You have dragged 5"
+    #assert dash_dcc.find_element("#out-drag-value").text == "You have dragged 5"
+    dash_dcc.wait_for_text_to_equal("#out-drag-value", "You have dragged 5")
 
     slider = dash_dcc.find_element("#slider")
     dash_dcc.click_and_hold_at_coord_fractions(slider, 0.25, 0.25)