First of all I should mention that this is an OS specific question. You will see this problem in Windows but not in Linux (I'm not sure about OS X, but maybe no problem there too.)
The problem with your code is not with the reading part.
If you open your
test.csv in Notepad++ you will see something like this:
If you edit it in Notepad++ so that it looks like
and then you run this:
testdf <- read.csv("test.csv",encoding="UTF-8")
You will see that there is no problem.
So in fact there are two problems:
When writing Unicode text, R changes it back to system locale and then again to unicode, that's why writing data to csv file does not work correctly.
R has problems showing Unicode data in
data.frame so even after reading it correctly,
testdf would print those codes there not the Unicode characters.
see this question on Writing Unicode Text into Text File from R (in Windows) in R mailing list archives,
and also this question on UTF-8 file output in R on stackoverflow.