Mock away document.createRange()

(cherry picked from commit a0e7e2075c)

spec/frontend/environment.js

@@ -38,6 +38,16 @@ class CustomEnvironment extends JSDOMEnvironment {
     this.global.fixturesBasePath = `${process.cwd()}/${
       IS_EE ? 'ee/' : ''
     }spec/javascripts/fixtures`;
+
+    // Not yet supported by JSDOM: https://github.com/jsdom/jsdom/issues/317
+    this.global.document.createRange = () => ({
+      setStart: () => {},
+      setEnd: () => {},
+      commonAncestorContainer: {
+        nodeName: 'BODY',
+        ownerDocument: this.global.document,
+      },
+    });
   }
 
   async teardown() {