add test to highlight #19307

packages/ember/tests/routing/substates_test.js

@@ -1,5 +1,7 @@
 import { RSVP } from '@ember/-internals/runtime';
 import { Route } from '@ember/-internals/routing';
+import Controller from '@ember/controller';
+
 import { moduleFor, ApplicationTestCase, runTask } from 'internal-test-helpers';
 
 let counter;
@@ -193,6 +195,77 @@ moduleFor(
       });
     }
 
+    ['@test Enter loading route with correct query parameters'](assert) {
+      let deferred = RSVP.defer();
+
+      this.router.map(function () {
+        this.route('dummy');
+      });
+
+      this.add(
+        'route:dummy',
+        Route.extend({
+          model() {
+            step(assert, 1, 'DummyRoute#model');
+            return deferred.promise;
+          },
+        })
+      );
+
+      this.add(
+        'controller:application',
+        class extends Controller {
+          queryParams = ['qux'];
+
+          qux = 'initial';
+        }
+      );
+
+      this.add(
+        'route:loading',
+        Route.extend({
+          setupController() {
+            step(assert, 2, 'LoadingRoute#setupController');
+          },
+        })
+      );
+      this.addTemplate('dummy', 'DUMMY');
+
+      return this.visit('/?qux=updated').then(() => {
+        assert.equal(
+          this.getController('application').qux,
+          'updated',
+          'the application controller has the correct qp value'
+        );
+
+        let promise = this.visit('/dummy?qux=updated').then(() => {
+          let text = this.$('#app').text();
+
+          assert.equal(text, 'DUMMY', `dummy template has been rendered`);
+          assert.equal(
+            this.getController('application').qux,
+            'updated',
+            'the application controller has the correct qp value'
+          );
+        });
+        assert.equal(this.currentPath, 'loading', `loading state entered`);
+        assert.equal(
+          this.currentURL,
+          '/dummy?qux=updated',
+          `during loading url reflect the correct state`
+        );
+        assert.equal(
+          this.getController('application').qux,
+          'updated',
+          'the application controller has the correct qp value'
+        );
+
+        deferred.resolve();
+
+        return promise;
+      });
+    }
+
     ['@test Slow promises returned from ApplicationRoute#model enter ApplicationLoadingRoute if present'](
       assert
     ) {