We need to update the following section to explain how tests should detect they are not running under a CI by stating what value $CI should be set to (if it should even be set...):

• https://github.com/kata-containers/tests/#detecting-a-ci-system

It's clear that if $CI == true we're running under a CI. But what is not clear atm is what $CI should be set to if we are not running under a CI. There seem to be three possibilities:

• $CI not set
• $CI set to empty string ("")
• $CI set to false

We do need to document two things:

• The expected value of $CI.
• How to test for "not running under a CI".

For the second bullet, should it be (which assumes $CI will be unset if not running under a CI):

if [ -z "$CI" ]; then
    echo "Not running under CI"
fi

Or should it be the following (which assumes will always be set to CI=false if not running under a CI):

if "$CI"; then
    echo "Not running under CI"
fi

I think the best option is for us to assume that the CI variable is not set if not running under a CI since that provides the least surprising and safest behaviour.