Fix

Author: pharret31

packages/devextreme/js/__internal/ui/stepper/stepper.ts

@@ -454,8 +454,8 @@ class Stepper extends CollectionWidgetAsync<StepperProperties> {
         this._invalidate();
         break;
       case 'items':
-        this._connector.option(this._getConnectorOptions());
         super._optionChanged(args);
+        this._connector.option(this._getConnectorOptions());
         break;
       default:
         super._optionChanged(args);

packages/devextreme/testing/tests/DevExpress.ui.widgets/stepper.tests.js

@@ -313,14 +313,18 @@ QUnit.module('Connector integration', moduleConfig, () => {
 
     QUnit.test('connector should update its size on items mutation (T1312793)', function(assert) {
         const items = [{}, {}];
-        this.reinit({ items });
+
+        this.reinit({ items, width: 100 });
 
         const sizeBefore = this.getConnector().option('size');
-        items.push({});
+
+        assert.roughEqual(sizeBefore, 50, 0.01, 'initial connector size is correct');
+
+        items.push({}, {});
         this.instance.option('items', items);
         const sizeAfter = this.getConnector().option('size');
 
-        assert.strictEqual(sizeAfter > sizeBefore, true, 'connector size is updated after items mutation');
+        assert.roughEqual(sizeAfter, 75, 0.01, 'connector size is correct after items mutation');
     });
 });