Copying longfilenames without retyping

$ ls -l thisismytestfile
-rw-r--r-- 1 Ajay None 13 Apr 17 03:22 thisismytestfile

Ajay@intel ~
$ cp thisismytestfile{,.bk}

Ajay@intel ~
$ ls -l thisismytest*
-rw-r--r-- 1 Ajay None 13 Apr 17 03:22 thisismytestfile
-rw-r--r-- 1 Ajay None 13 Apr 17 03:26 thisismytestfile.bk