[R] Transform variable number of rows per subject to column variables?

[Bing Ho]

Hello,

I am very new to R, but I am having trouble with my dataset.

I have a data frame where a subject has a variable number of multiple 
observations for each row, which I wish the transform these 
observations to column variables.

An example of the data frame
ID 	TEST.A	TEST.B
1	10	1
1	13	2
1	11	1
2	15	2
2	17	3

And I wish to transform it to the following:
ID	TEST.A1	TEST.A2	TEST.A3	TEST.B1	TEST.B2	TEST.B3
1	10		13		11		1		2		1
2	15		17		NA		2		3		NA

In other words, for the variable number of repeated follow up 
studies, a new column variable for each subject, but they are grouped 
by the original test.

Thank you for any help - I'm realizing that I am a terrible programmer!

Bing Ho