A quick and clean way to write end-to-end testcases for command line utilities is the cram testing framework. You can install cram using pip install cram (or inside virtualenv), and then create a file called test1.t with the following contents:

The first testcase

  $ echo abc

  $ echo -e 'a\nb\nc' | wc -l

Launch /bin/false and verify that it exits with exit code 1

  $ /bin/false

Launch sub-shell and verify that it exits with exit code 42

  $ (echo abc ; exit 42)

cram will verify that exit code is 0 if no expected exit code N is written as [N]

  $ true

Testcases will be skipped if do you do "exit 80"

  $ echo abc && exit 80

cram can also invoke multiline commands

  $ cat /proc/cpuinfo | grep bogo | \
  > cut -f 2 -d : | \
  > awk '{s+=$1} END {print s}' | \
  > wc -l

You can also invoke multiple commands

  $ export ABC=def
  $ echo $ABC

You can then run the test using cram test1.t. Another nice feature is the interactive mode where you can automatically make the actual output become the expected output (i.e. just like snapshot testing in jest).

Writing tests with cram is extremely powerful because you have all your regular command line tools available. For example, you can curl some API and assert that the response looks reasonable.

Kudos to Brodie Rao for creating this awesome tool!