How to prevent Ruby's test/unit library from autorunning your tests

19 February 2012

Today I had a situation where I wanted to use perftools.rb to profile a test suite, which was written with Ruby’s test/unit library.

test/unit installs an at_exit hook which runs all the tests before Ruby exits. This was problematic, because it meant that all the tests ran after perftools had already finished its profile.

So I wanted to turn off the autorunning and explicitly run the test suite. I found out how to monkey-patch test/unit to achieve this, and figured it might be useful to someone in the future, so:

Ruby 1.9

require 'test/unit'

class Test::Unit::Runner
  @@stop_auto_run = true
end

class FooTest < Test::Unit::TestCase
  def test_foo
    assert true
  end
end

Test::Unit::Runner.new.run(ARGV)

Ruby 1.8

require 'test/unit'

module Test::Unit
  def self.run?; true; end
end

class FooTest < Test::Unit::TestCase
  def test_foo
    assert true
  end
end

Test::Unit::AutoRunner.run