message: Refer to the testing best practices guide from contribution guide
diff: @@ -88,6 +88,9 @@ TensorFlow coding style.
  submitting PRs to fix one typo, one warning,etc. We recommend fixing the
  same issue at the file level at least (e.g.: fix all typos in a file, fix
  all compiler warning in a file, etc.)
  +* Tests should follow the
  + [testing best practices](https://www.tensorflow.org/community/contribute/tests)
  + guide.
  #### License
  