Command Test

Test that your app runs or does not run commands.

Why?

Ruby has a bucket of ways to run commands:

• Kernel#system
• Kernel#`
• Kernel.open
• IO.popen
• Open3.popen3

Mocking becomes impractical because you seldom care how a command is run, just that it is run (or not run). Methods that run the command through the shell are also tricky to mock correctly, as extra shell syntax can easily throw off the test.

How

RSpec

lambda do
  ...
end.should run_command('convert', 'bad.gif', 'good.png')

Test::Unit

assert_runs_command 'convert', 'bad.gif', 'good.png' do
  ...
end

assert_does_not_run_command 'convert', 'bad.gif', 'good.png' do
  ...
end

Other frameworks

Not really using them myself, but I'll bet they're easy to add. Patch me and be famous!

Tricks

Regexps

You can match arguments against regexps:

lambda do
  ...
end.should run_command('convert', /.gif\z/, /.png\z/)

Wildcards

An integer, n, matches any n arguments:

lambda do
  system 'diff', 'old.txt', 'new.txt')
end.should run_command('diff', 2)

An range matches any number of arguments in that range:

lambda do
  system 'diff', '-w', 'one.txt', 'two.txt', 'three.txt'
end.should run_command('diff', '-w', 2..3)

:* matches any number of arguments:

lamdba do
  system 'hostname'
end.should run_command('convert', :*, 'target.png')

:+ matches at least one argument:

lamdba do
  system 'hostname'
end.should run_command('gem', 'install', :+)

Any combination of wildcards can be used together.

Recording

You can record the commands run during a block:

commands = CommandTest.record do
  system 'convert', 'bad.gif', 'good.png'
  system 'identify', 'good.png'
end
commands # [['convert', 'bad.gif', 'good.png'], ['identify', 'good.png']]

And then match them yourself:

CommandTest.match?(commands.first, ['convert', :*])

You can use this to check that commands were run in a certain order, a certain number of times, in a pretty pattern, ... the possibilities are endless!

Contributing

• Bug reports: http://github.com/oggy/command_test/issues
• Source: http://github.com/oggy/command_test
• Patches: Fork on Github, send pull request.
  • Ensure patch includes tests.
  • Leave the version alone, or bump it in a separate commit.

Copyright

Copyright (c) 2010 George Ogata. See LICENSE for details.