Example

$ ls -l
AndroidTest.pdf
Angular2Test.pdf
BashTest.pdf

The simplest way to remove ‘Test’ from any files:

rename 's/Test//g' *.pdf
$ ls -l
Android.pdf
Angular2.pdf
Bash.pdf

Or change ‘Test’ to ‘Hello’

rename 's/Test/Hello/g' *.pdf
$ ls -l
AndroidTest.pdf
Angular2Test.pdf
BashTest.pdf