Function in rep() function

Question

Why is

rep(message("TEST"),3)
rep(c(message("TEST")),3)

>
TEST
NULL
> 

not the same as

c(message("TEST"),message("TEST"),message("TEST"))

>
TEST
TEST
TEST
NULL
> 

How do I then get the second result using the rep() function?

EDIT:

Very "conveniently" we could use:

invisible(lapply((rep(c(quote(message("TEST"))),3)),eval))
> 
TEST
TEST
TEST
> 

Answer 1

From ?rep:

‘rep’ replicates the values in ‘x’.

The value from message("TEST") is NULL.

You can check this with e.g.

m <- message("TEST");
m;
#NULL
rep(m, 3);
#NULL
rep(NULL, 3);
#NULL

As to your second question, see @docendodiscimus' comment.