const formatStack = (thrown: Thrown | null) =>
  thrown === null || !thrown.isError
    ? ''
    : formatStackTrace(
        separateMessageFromStack(thrown.value.stack!).stack,
        {
          rootDir: process.cwd(),
          testMatch: [],
        },
        {
          noStackTrace: false,
        },
      );

  private _logFormattedReferenceError(errorMessage: string) {
    const originalStack = new ReferenceError(errorMessage)
      .stack!.split('\n')
      // Remove this file from the stack (jest-message-utils will keep one line)
      .filter(line => line.indexOf(__filename) === -1)
      .join('\n');

    const {message, stack} = separateMessageFromStack(originalStack);

    console.error(
      `\n${message}\n` +
        formatStackTrace(stack, this._config, {noStackTrace: false}),
    );
  }

 private _checkFakeTimers() {
   if (this._global.setTimeout !== this._fakeTimerAPIs.setTimeout) {
     this._global.console.warn(
       `A function to advance timers was called but the timers API is not ` +
         `mocked with fake timers. Call \`jest.useFakeTimers()\` in this ` +
         `test or enable fake timers globally by setting ` +
         `\`"timers": "fake"\` in ` +
         `the configuration file. This warning is likely a result of a ` +
         `default configuration change in Jest 15.\n\n` +
         `Release Blog Post: https://jestjs.io/blog/2016/09/01/jest-15.html\n` +
         `Stack Trace:\n` +
         formatStackTrace(new Error().stack!, this._config, {
           noStackTrace: false,
         }),
     );
   }
 }