In Ruby's Test::Unit::TestCase, how do I override the initialize method?

Question

I\'m struggling with Test::Unit. When I think of unit tests, I think of one simple test per file. But in Ruby\'s framework, I must instead write:

class M         


        

Answer 1

+1 for the RSpec answer above by @orion-edwards. I would have commented on his answer, but I don't have enough reputation yet to comment on answers.

I use test/unit and RSpec a lot and I have to say ... the code that everyone has been posting is missing a very important feature of before(:all) which is: @instance variable support.

In RSpec, you can do:

describe 'Whatever' do
  before :all do
    @foo = 'foo'
  end

  # This will pass
  it 'first' do
    assert_equal 'foo', @foo
    @foo = 'different'
    assert_equal 'different', @foo
  end

  # This will pass, even though the previous test changed the 
  # value of @foo.  This is because RSpec stores the values of 
  # all instance variables created by before(:all) and copies 
  # them into your test's scope before each test runs.
  it 'second' do
    assert_equal 'foo', @foo
    @foo = 'different'
    assert_equal 'different', @foo
  end
end

The implementations of #startup and #shutdown above all focus on making sure that these methods only get called once for the entire TestCase class, but any instance variables used in these methods would be lost!

RSpec runs its before(:all) in its own instance of Object and all of the local variables are copied before each test is run.

To access any variables that are created during a global #startup method, you would need to either:

• copy all of the instance variables created by #startup, like RSpec does
• define your variables in #startup into a scope that you can access from your test methods, eg. @@class_variables or create class-level attr_accessors that provide access to the @instance_variables that you create inside of def self.startup

Just my $0.02!

Answer 2

Use the TestSuite as @romulo-a-ceccon described for special preparations for each test suite.

However I think it should be mentioned here that Unit tests are ment to run in total isolation. Thus the execution flow is setup-test-teardown which should guarantee that each test run undisturbed by anything the other tests did.

Answer 3

I created a mixin called SetupOnce. Here's an example of using it.

require 'test/unit'
require 'setuponce'


class MyTest < Test::Unit::TestCase
  include SetupOnce

  def self.setup_once
    puts "doing one-time setup"
  end

  def self.teardown_once
    puts "doing one-time teardown"
  end

end

And here is the actual code; notice it requires another module available from the first link in the footnotes.

require 'mixin_class_methods' # see footnote 1

module SetupOnce
  mixin_class_methods

  define_class_methods do
    def setup_once; end

    def teardown_once; end

    def suite
      mySuite = super

      def mySuite.run(*args)
        @name.to_class.setup_once
        super(*args)
        @name.to_class.teardown_once
      end

      return mySuite
    end
  end
end

# See footnote 2
class String
  def to_class
    split('::').inject(Kernel) {
      |scope, const_name|
      scope.const_get(const_name)
    }
  end
end

Footnotes:

1. http://redcorundum.blogspot.com/2006/06/mixing-in-class-methods.html

2. http://infovore.org/archives/2006/08/02/getting-a-class-object-in-ruby-from-a-string-containing-that-classes-name/

Answer 4

As mentioned in Hal Fulton's book "The Ruby Way". He overrides the self.suite method of Test::Unit which allows the test cases in a class to run as a suite.

def self.suite
    mysuite = super
    def mysuite.run(*args)
      MyTest.startup()
      super
      MyTest.shutdown()
    end
    mysuite
end

Here is an example:

class MyTest < Test::Unit::TestCase
    class << self
        def startup
            puts 'runs only once at start'
        end
        def shutdown
            puts 'runs only once at end'
        end
        def suite
            mysuite = super
            def mysuite.run(*args)
              MyTest.startup()
              super
              MyTest.shutdown()
            end
            mysuite
        end
    end

    def setup
        puts 'runs before each test'
    end
    def teardown
        puts 'runs after each test'
    end 
    def test_stuff
        assert(true)
    end
end

Answer 5

That's how it's supposed to work!

Each test should be completely isolated from the rest, so the setup and tear_down methods are executed once for every test-case. There are cases, however, when you might want more control over the execution flow. Then you can group the test-cases in suites.

In your case you could write something like the following:

require 'test/unit'
require 'test/unit/ui/console/testrunner'

class TestDecorator < Test::Unit::TestSuite

  def initialize(test_case_class)
    super
    self << test_case_class.suite
  end

  def run(result, &progress_block)
    setup_suite
    begin
      super(result, &progress_block)      
    ensure
      tear_down_suite
    end
  end

end

class MyTestCase < Test::Unit::TestCase

  def test_1
    puts "test_1"
    assert_equal(1, 1)
  end

  def test_2
    puts "test_2"
    assert_equal(2, 2)
  end

end

class MySuite < TestDecorator

  def setup_suite
    puts "setup_suite"
  end

  def tear_down_suite
    puts "tear_down_suite"
  end

end

Test::Unit::UI::Console::TestRunner.run(MySuite.new(MyTestCase))

The TestDecorator defines a special suite which provides a setup and tear_down method which run only once before and after the running of the set of test-cases it contains.

The drawback of this is that you need to tell Test::Unit how to run the tests in the unit. In the event your unit contains many test-cases and you need a decorator for only one of them you'll need something like this:

require 'test/unit'
require 'test/unit/ui/console/testrunner'

class TestDecorator < Test::Unit::TestSuite

  def initialize(test_case_class)
    super
    self << test_case_class.suite
  end

  def run(result, &progress_block)
    setup_suite
    begin
      super(result, &progress_block)      
    ensure
      tear_down_suite
    end
  end

end

class MyTestCase < Test::Unit::TestCase

  def test_1
    puts "test_1"
    assert_equal(1, 1)
  end

  def test_2
    puts "test_2"
    assert_equal(2, 2)
  end

end

class MySuite < TestDecorator

  def setup_suite
    puts "setup_suite"
  end

  def tear_down_suite
    puts "tear_down_suite"
  end

end

class AnotherTestCase < Test::Unit::TestCase

  def test_a
    puts "test_a"
    assert_equal("a", "a")
  end

end

class Tests

  def self.suite
    suite = Test::Unit::TestSuite.new
    suite << MySuite.new(MyTestCase)
    suite << AnotherTestCase.suite
    suite
  end

end

Test::Unit::UI::Console::TestRunner.run(Tests.suite)

The Test::Unit documentation documentation provides a good explanation on how suites work.

Answer 6

Well, I accomplished basically the same way in a really ugly and horrible fashion, but it was quicker. :) Once I realized that the tests are run alphabetically:

class MyTests < Test::Unit::TestCase
def test_AASetup # I have a few tests that start with "A", but I doubt any will start with "Aardvark" or "Aargh!"
    #Run setup code
end

def MoreTests
end

def test_ZTeardown
    #Run teardown code
end

It aint pretty, but it works :)