I'm not aware of any way to automatically test for regressions with issues such as as bug 4393, rdar:// 4094066 or bug 4699. These seem to happen from time to time (the first two are regressions themselves), so having such a facility should be beneficial.
Created attachment 4222 [details] TextInputController implementation A first cut at implementing this facility. I haven't managed to test for regressions in form controls (they don't want to take focus when running from DumpRenderTree), and haven't implemented NSAttributedString support, but this should already be quite useful for testing contentEditable text.
Created attachment 4223 [details] test the controller functionality
Comment on attachment 4222 [details] TextInputController implementation Looks good. Soon we might want to start breaking this tool up into multiple files.
Landed this in a separate file.