How Package Reliability is Checked by CRAN

I am teaching R since years. In a previous day lecture one of the participant asked a very important question. Since a lot of community members are contributing into R platform. What is criteria or system to check the package is performing consistently well. Means the results of functions are reliable. I know some of the policy related to package submission to CRAN. But I would specifically want to know is there any rating system for packages, how package results reliability is checked. Also we have packages that are provided in zip folders which are not part of the CRAN project. How can we ensure the confidence in using such packages?

Regards
Usman

Hi @usmanmarwat , CRAN runs what it is called "checks" which involves installation and running all of the package tests, and against several different operating systems. The results are publicly available, here is the link for the current results of ggplot2: CRAN Package Check Results for Package ggplot2

Regarding non-CRAN packages, as in the ones you get in a zip folder, since you have the source code, you should be able to open them in RStudio, and run the same checks CRAN does. In other words, it would be up to you to actually run the tests and verify the code.

Hope this helps.