Merge branch 'winh-jest-wrong-file-error' into 'master'

Show error if Jest is used with Karma files

See merge request gitlab-org/gitlab!17019

jest.config.js

@@ -63,3 +63,15 @@ module.exports = {
     IS_EE,
   },
 };
+
+const karmaTestFile = process.argv.find(arg => arg.includes('spec/javascripts/'));
+if (karmaTestFile) {
+  console.error(`
+Files in spec/javascripts/ and ee/spec/javascripts need to be run with Karma.
+Please use the following command instead:
+
+yarn karma -f ${karmaTestFile}
+
+`);
+  process.exit(1);
+}