run() {
    // The base mocha.run will not load files, see loadFiles() override.
    return this.importFiles().then(() => {
      return new Promise((resolve, reject) => {
        super.run((numberOfFailures) => {
          numberOfFailures ? reject(numberOfFailures) : resolve();
        })
      });
    });
  }
Run tests
@return {Runner}
@api public