Why is this command not found? I have a simple shell script:

#!/bin/bash
echo test


I can execute script successfully as:

./test.sh


and

source ./test.sh


However, the following throws an error:

. ./test.sh


error:

.: Command not found.


What could be causing the error? This works on el capitan but not on sierra.

I'm running macOS 10.12.3 with the default terminal.

Thanks!

EDIT: I've rewritten the question in order to simplify it with a small test script rather than my actual production script - this shows that the issue is the execution environment rather than the script.
It turns out that my default shell was set to CSH which does not support:

. ./


I have switched the default shell to bash and this now works. I think the default shell as changed when my company imaged the MacBook or this is now the default with a fresh install of Sierra.

I will accept this as the answer after the 2 days stackexchange waiting period.