I’ve written many ruby gems that have binaries, generally with commander for the command-line interface. I was trying to increase the test coverage on those gems when I realized that it’s tricky to test the parts are integrated with commander.
This is what a common commander setup looks like:
require 'rubygems'
require 'commander/import'
program :name, 'Foo Bar'
program :version, '1.0.0'
program :description, 'Stupid command that prints foo or bar.'
command :foo do |c|
# ...
end
Requiring that file from your gem’s binary does the trick.
#!/usr/bin/env ruby
require File.join(
File.dirname(__FILE__), '..', 'lib', 'program'
)
Outstanding.
The main problem for testing is that this is meant for automatic execution. The
commander/import require runs commander on exit as soon as it’s finished
loading the file. But for testing, you want to run commander in a test, not when
the file is required. And you definitely don’t want to have to play with
un-requiring files to run it multiple times.
What you need is to have the commander program available as an object that you
can test at will with any arguments. To achieve that, I looked at what
commander/import does:
require 'commander'
require 'commander/delegates'
include Commander::UI
include Commander::UI::AskForClass
include Commander::Delegates
# ...
at_exit { run! }
What Commander::Delegates does is forward most commander methods (e.g.
program, command) to a singleton Commander::Runner instance. So let’s do
the same thing with a runner of our own.
require 'commander'
module FooBar
class Program < Commander::Runner
include Commander::UI
include Commander::UI::AskForClass
# No need to include Commander::Delegates,
# as we're a Commander::Runner already.
def initialize argv = ARGV
super argv
program :name, 'Foo Bar'
program :version, '1.0.0'
program :description,
'Stupid command that prints foo or bar.'
command :foo do |c|
# ...
end
end
end
end
You can now test your commander program to your heart’s content.
# test result
program = FooBar::Program.new custom_args
program.run!
expect(File.exists?('some file')).to be_true
# test errors
program = FooBar::Program.new bad_args
expect{ program.run! }.to raise_error(FooBar::Error)
# test output
program = FooBar::Program.new custom_args
stdout, stderr = StringIO.new, StringIO.new
$stdout, $stderr = stdout, stderr
program.run!
$stdout, $stderr = STDOUT, STDERR
expect(stdout.string.chomp("\n")).to eq('some output')
expect(stderr.string).to be_empty
Note that your binary must now run the commander program.
#!/usr/bin/env ruby
require File.join(
File.dirname(__FILE__), '..',
'lib', 'foo_bar', 'program'
)
FooBar::Program.new.run!
Unfortunately that doesn’t cover user interaction, but I don’t know how to test that yet. I will probably write another article when the time comes. In the meantime, enjoy.