Calling (invoking) rails rake tasks from within ruby, for testing, try 2

Tim Connor — Thu, 21 Feb 2008 13:48:00 -0800

Yesterday I wrote a post on capturing the output of rake from a ruby call using backticks, because I wanted to do so in a test. Well, I had Date.today stubbed out, but got lazy and used yesterday’s date, so of course when I come in today the test fails. In the light of a new day my problem was obvious. If you call rake from a sub-shell, say via ``, of course your mocking will not exist in that process. So today, I had Another Wonderful Opportunity for Learning (there are acronyms for this that use a different word than wonderful): a chance to do it right.

It took a little digging to figure out how to get this to work right with the built-in rails tasks, so here you go:


require 'rake'
require 'rake/rdoctask'
require 'rake/testtask'
require 'tasks/rails'

def capture_stdout
  s = StringIO.new
  oldstdout = $stdout
  $stdout = s
  yield
  s.string
ensure
  $stdout = oldstdout
end

Rake.application.rake_require '../../lib/tasks/metric_fetcher'
results = capture_stdout {Rake.application['metric_fetcher'].invoke}

I liberated capture_stdout from the rake tests themselves. In retrospect, I should have just looked there first. As TDD and especially BDD get even more widespread the tests are often the easiest place to look for good examples of usage.

a timocracy of one: Calling (invoking) rails rake tasks from within ruby, for testing, try 2

Calling (invoking) rails rake tasks from within ruby, for testing, try 2