PaulBarry.com - A Ruby Test Framework in One Line

A Ruby Test Framework in One Line

2008-05-23T11:17:48-04:00

Time for a little Friday fun with Ruby. I love Ruby for things like this. I realize this has little practical usage, but the fact that it's possible says a lot about the language. You can build a test "framework" in one line of code in Ruby. Let's say we are going to write a method that take 0 to n arguments and adds them up. So following TDD, we write the tests first:

tests = {
  "sum" => 0,
  "sum(7)" => 7,
  "sum(2, 3)" => 5,
  "sum(2, 3, 5)" => 10
}

The tests are defined in a hash where the key is the code to be tested in a string and the value is the expected result. Next we write our implementation:

def sum(*args)
  (args || 0).inject(0){|s,e| s+e}
end

And finally, we create and execute our test framework in one line of code:

tests.each{|e,v| puts((r=eval(e))==v ? ". #{e}" : "! #{e} was '#{r}', expected '#{v}'")}

The output looks like this:

. sum
. sum(2, 3, 5)
. sum(7)
. sum(2, 3)

If we change one of our tests to show a failure, you get this:

. sum
. sum(2, 3, 5)
. sum(7)
! sum(2, 3) was '5', expected '8'

Comment on "A Ruby Test Framework in One Line" by Ryan Davis

2008-05-23T19:19:41-04:00

cute! I like the simplicity of the runner.

But your impl looks flawed.... shouldn't it be:

args.inject(0) {|s,e| s+e}

the || 0 part would only help you if you explicitly passed in nil or false. You might as well blow up if they're passing in bad data.

Comment on "A Ruby Test Framework in One Line" by Paul Barry

2008-05-23T21:09:03-04:00

@Ryan

Good point, for some reason I was thinking that passing no args would mean that args would be nil, but it is an empty array. I think this is the right implementation:

args.inject(0){|s,e| s+e.to_i}

Which allows sum(nil, "1", 2) to return 3, which of course I was easily able to add a test for. Yay for TDD!

Comment on "A Ruby Test Framework in One Line" by François Vaux

2008-05-30T05:23:09-04:00

Nice one-liner :-)

I've been inspired by this and built a more robust one, but it's 20 lines long :P

def MTest(tests)
if tests[0].is_a?(String) then puts tests.shift end
threads = []
results = {:pass => 0, :fail => 0, :err => 0}
tests.each do |t|
e,p,v = *t
threads << Thread.new do
begin
puts(if (r = p.call) == v
results[:pass] += 1
". #{e}"
else
results[:fail] += 1
"! #{e} was #{r}, expected #{v}"
end)
rescue => x
results[:err] += 1
puts "@ #{x.class} at line #{x.backtrace[0].split(':')[1]}"
end
end
end
threads.join
results
end

This allows you many tricks like naming your tests, don't abort on exceptions but show a notice and get a summary for your tests.

Comment on "A Ruby Test Framework in One Line" by François Vaux

2008-05-30T05:25:09-04:00

I forgot to notice that the test format is now as follows :

tests = [
  "= Some Basic Tests =",
  ['true', proc { true }, true],
  ['true', proc { false }, true],
  ['sum(2,5)', proc { sum(2,5) }, 7]
]

And you just have to call MTest(tests)

(sorry for screwing the indent in my last post)

Comment on "A Ruby Test Framework in One Line" by Kerry Gunther

2008-08-05T15:55:53-04:00

outstanding!