leah blogs

January 2007

24jan2007 · Announcing test/spec 0.3, a BDD interface for Test::Unit

Today I’m releasing test/spec 0.3, a library to do BDD with Test::Unit.

(See below for changes in version 0.3.)

What is test/spec?

test/spec layers an RSpec-inspired interface on top of Test::Unit, so you can mix TDD and BDD (Behavior-Driven Development).

test/spec is a clean-room implementation that maps most kinds of Test::Unit assertions to a ‘should’-like syntax.

Consider this Test::Unit test case:

class TestFoo < Test::Unit::TestCase
  def test_should_bar
    assert_equal 5, 2 + 3

In test/spec, it looks like this:

require 'test/spec'

context "Foo" do
  specify "should bar" do
    (2 + 3).should.equal 5

test/spec does not include a mocking/stubbing-framework; use whichever you like to—FlexMock and Mocha have been tested.

test/spec has no dependencies outside Ruby 1.8.

Mixing test/spec and test/unit

test/spec and Test::Unit contexts/test cases can be intermixed freely, run in the same test and live in the same files. You can just add them to your Rake::TestTask, too. test/spec allows you to leverage your full existing Test::Unit infrastructure.

test/spec does not change Test::Unit with the exception of monkey-patching Test::Unit::TestSuite to order the test cases before running them. (This should not do any harm, but if you know a way around it, please tell me.)

Wrapped assertions

  • assert_equal: should.equal, should ==
  • assert_not_equal: should.not.equal, should.not ==
  • assert_same: should.be
  • assert_not_same: should.not.be
  • assert_nil: should.be.nil
  • assert_not_nil: should.not.be.nil
  • assert_in_delta: should.be.close
  • assert_match: should.match, should =~
  • assert_no_match: should.not.match, should.not =~
  • assert_instance_of: should.be.an.instance_of
  • assert_kind_of: should.be.a.kind_of
  • assert_respond_to: should.respond_to
  • assert_raise: should.raise
  • assert_nothing_raised: should.not.raise
  • assert_throws: should.throw
  • assert_nothing_thrown: should.not.throw
  • assert_block: should.satisfy

Additional assertions

These assertions are not included in Test::Unit, but have been added to test/spec for convenience:

  • should.not.satisfy
  • a.should.predicate (works like assert a.predicate?)
  • a.should.be operator (where operator is <, <=, >, >=, or ===)
  • should.output, to check what is printed


With more complex assertions, it may be helpful to provide a message to show if the assertion has failed. This can be done with the Should#blaming or Should#messaging methods:

RUBY_VERSION.should.messaging("Ruby too old.").be > "1.8.4"

(1 + 1).should.blaming("weird math").not.equal 11

Custom shoulds (“Matchers”)

To capture recurring patterns in parts of your specifications, you can define custom “shoulds” (RSpec calls them “matchers”) in your contexts, or include modules of them:

context "Numbers"
  class EqualString < Test::Spec::CustomShould
    def matches?(other)
      object == other.to_s

  def equal_string(str)

  specify "should have to_s"
    42.should equal_string("42")

Alternatively, your implementation can define CustomShould#assumptions, where you can use test/spec assertions instead of Boolean predicates:

class EqualString < Test::Spec::CustomShould
  def assumptions(other)
    object.should.equal other.to_s

A CustomShould by default takes one argument, which is placed in self.object for your convenience.

You can CustomShould#failure_message to provide a better error message.

SpecDox and RDox

test/spec adds two additional test runners to Test::Unit, based on the console runner but with a different output format.

SpecDox, run with --runner=specdox (or -rs) looks like RSpec’s output:

- works for print
- works for puts
- works with readline

RDox, run with --runner=rdox (or -rr) can be included for RDoc documentation:

== spec.output
* works for print
* works for puts
* works with readline

SpecDox and RDox work for Test::Unit too:

$ ruby -r test/spec test/testunit/test_testresult.rb -rs

- fault notification
- passed?
- result changed notification

Finished in 0.106647 seconds.

3 specifications (30 requirements), 0 failures

Disabled specifications

Akin to the usual Test::Unit practice, tests quickly can be disabled by replacing specify with xspecify. test/spec will count the disabled tests when you run it with SpecDox or RDox.


Since version 0.2, test/spec features a standalone test runner called specrb. specrb is like an extended version of testrb, Test::Unit’s test runner, but has additional options. It can be used for plain Test::Unit suites, too.

$ specrb -a -s -n should.output

- works for print
- works for puts
- works with readline

Finished in 0.162571 seconds.

3 specifications (6 requirements), 0 failures

See specrb --help for the usage.

Changes in version 0.3

  • should.be_close, should.be_an_instance_of, should.be_a_kind_of, and should.be_nil have been deprecated. Use the dot-variants of them. These assertions will be removed in 1.0.
  • specrb -a now includes -Ilib by default for easier out-of-the-box testing.
  • Added custom shoulds.
  • Added messaging/blaming.
  • Added disabling of specifications.
  • Small bug fixes.
  • Gem available.

Installing with RubyGems

Since version 0.3, a Gem of test/spec is available. You can install with:

gem install test-spec

(It may take some time for the index to be updated and the mirrors propagated.) I also provide a local mirror of the gems (and development snapshots) at my site:

gem install test-spec --source http://chneukirchen.org/releases/gems


Version 1.0 (February 2006): first stable release.


Please mail bugs, suggestions and patches to chneukirchen@gmail.com.

Darcs repository (“darcs send” is welcome for patches):

Thanks to

  • Eero Saynatkari for writing should.output.
  • Jean-Michel Garnier for packaging the first gem.
  • Mikko Lehtonen, Jan Wikholm, Matt Mower and Michael Fellinger for testing the gem.
  • Thomas Fuchs for script.aculo.us BDD testing which convinced me.
  • Dave Astels for BDD.
  • The RSpec team for API inspiration.
  • Nathaniel Talbott for Test::Unit.


Copyright (C) 2006, 2007 Christian Neukirchen
test/spec is licensed under the same terms as Ruby itself.

Where can I get it?

You can download test/spec 0.3 at:

Alternatively, you can checkout from the development repository with:

darcs get http://chneukirchen.org/repos/testspec

(Patches using “darcs send” are most welcome.)

Happy hacking and have a nice day,
Christian Neukirchen

ea043ab5837994179d4659aa1e2fcc88  test-spec-0.3.0.tar.gz
d0e1c45c2e814cc26a7967232ca99f6c  test-spec-0.3.0.gem

NP: The Rolling Stones—Gimmie Shelter

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