Introduction
echo(1) is a Unix command line tool, which writes its command line
arguments to the standard output. This is a simple acceptance test
suite for the echo implementation.
For more information, see [@foo2020].
No arguments
Run echo without arguments.
when user runs echo without arguments
then exit code is 0
then standard output contains a newline
then standard error is empty
Hello, world
This scenario runs echo to produce the output "hello, world".
when user runs echo with arguments hello, world
then exit code is 0
then standard output contains "hello, world"
then standard error is empty