All of these will get you pretty far toward, with more confidence in your visualizations, but another step you can take to be even more of a rockstar is to add automated testing to your projects.
There are many reasons to write automated tests: if you have a product that has to reliably render charts, and the chart is rendering merely a part of a much larger application, you likely want to use automated testing to ensure that changes to the application don't break your charts. Likewise, if you've created an open source project that receives a lot of pull requests from various people who use your library, you might want tests to ensure that none of this outside code causes regressive bugs. Beyond that, automated tests are great if you want to be able to show your editor proof that your chart is working and accurate, or if you merely want to have more confidence in your data visualization work.
There are fundamentally two ways you can approach...