Answers for "when to do manual testing"

what is manual testing

Literally, it means testing an application with your hands. 
It is performed by humans, no tools or codes are used.

when to do manual testing

-Unstable test cases
-Tests that you will only run only once.
-The only exception to this rule is that
if you want to execute a test with a very large 
set of data, even if it’s only once,
then it makes sense to automate it.
-Unfinished functionality
-Visual test cases
-Also Tests that need to be run ASAP
which usually a new feature which is
developed requires a quick feedback
so testing it manually at first making sense.