Introduction
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**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
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Run `echo` without arguments.
```scenario
when user runs echo without arguments
then exit code is 0
then standard output contains a newline
then standard error is empty
```
Hello, world
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This scenario runs `echo` to produce the output "hello, world".
```scenario
when user runs echo with arguments hello, world
then exit code is 0
then standard output contains "hello, world"
then standard error is empty
```
# References