Stronger Testing Procedures

[caloon]

This is not a specific issue, but more of a general feedback. I am a big fan of this repository and have been since the very early days. However, it is my impression that changes to the code base, especially pull requests submitted by the community, are accepted without applying strong testing procedures. I'd like to make the case for this by explaining my situation:

• Version 3.2.1 was a stable version for me (I am only using line and scatter charts in a relatively simple manner)
• With version 3.2.2 the chart renderers were refactored (3164). However, the changes caused the first circle on line charts to disappear (3915).
• Version 3.3.0 meant to fix the issue with the circles, by using a new iterator (3891). Yet, this caused a much greater issue, leading to many reports of app crashes (compare 4049). These app crashes are also rather frequent, with more than 5% of users of my app experiencing it.

As a result, version 3.2.1 is the last stable release which is suitable for use in my app.

[liuxuan30]

We have UT and CI, and I would apology for the issue.

But asking every PR to include UT sounds a little unrealistic. And some PRs are just hard to have a UT, like animation or some other changes, somehow it escape our UT.

Thanks for your support, I will try to take a look at issues you mentioned.