Better test conditional.

I was trying to separate arguments to preserve their values with quotes
instead of using the more appropriate "${@}" convention.
Must source functions at the beginning of each test.
More appropriate to remove tmp files when finished.
Add tmp file tests.
Report how long tests took.
Change DO_CUSTOM_CMD to DO_CUSTOM for simplicity.
Change DEFAULT_WORK_LENGTH test to realistic value.
Don't run vsleep in a subshell.

There is no reason to run vsleep in a subshell in this instance and the
$left variable needs to be set for the ctrl_c function to operate
properly on the following test.
Add tests for do_options logic.