Create AND Switch:

git switch -c testing
This will also move uncommitted work to the new branch.

Create:

git branch testing

Switching:

git switch testing

Rename local (unpushed):

git branch -m newname

or on very old machines:
git checkout testing

List branches:

git branch

Merge:

First switch to the branch you'd like to merge into. Then:
git merge testing

Delete:

Local

git branch -d testing

Remote

git push origin --delete testing