Helpful Additions To Test::Unit

March 6th, 2007

Doing a lot of rails work, I’m getting a good feel for testing in ruby and rails. Here are some tricks / snippets I use :

assert_raises takes a string and/or a class

I want to be able to write

one = Project.new('one')

projects << one      
assert_raises('project named "one" already exists') do
  projects << one
end

I’ve done this a few times, but I think cruisecontrol.rb’s implementation is the most robust :

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  def assert_raises(arg1 = nil, arg2 = nil)
    expected_error = arg1.is_a?(Exception) ? arg1 : nil
    expected_class = arg1.is_a?(Class) ? arg1 : nil
    expected_message = arg1.is_a?(String) ? arg1 : arg2
    begin 
      yield
      fail "expected error was not raised"
    rescue Test::Unit::AssertionFailedError
      raise
    rescue => e
      raise if e.message == "expected error was not raised"
      assert_equal(expected_error, e) if expected_error
      assert_equal(expected_class, e.class, "Unexpected error type raised") if expected_class
      assert_equal(expected_message, e.message, "Unexpected error message") if expected_message.is_a? String
      assert_matched(expected_message, e.message, "Unexpected error message") if expected_message.is_a? Regexp
    end
  end

assert_equal_sets

In Java, I used to push things into sets and compare them when I didn’t care about order. In ruby, I sometimes use assert_equal_sets. It does a compare of two arrays independent of order. So

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  assert_equal_sets [1, 3, 5], [3, 5, 1]   # passes
  assert_equal_sets [2, 3], [3, 4]    # fails
 
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class Array
  def reorder_like!(other)
    tmp = dup
    clear
    other.each {|x| self << tmp.delete(x) if tmp.index x}
    tmp.each {|x| self << x }
  end
end

class Test::Unit::TestCase
  def assert_equal_sets(expected, actual)
    actual.reorder_like!(expected)
    assert_equal(expected, actual)
  end
end

file_sandbox for testing against the file system

After dragging this code around me for the last 6 or 7 projects I’ve been on, I finally packaged it up as a gem . It lets you write code like :

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in_sandbox do |sandbox|
  sandbox.new :file => 'b/a.txt', :with_contents => 'some stuff'

  assert_equal 'some_stuff', File.read(sandbox.root + '/b/a.txt')
end

Basically it creates a temporary directory for you to muck about in. After the block is ended (or teardown is called on your test) that directory and everything in it is guaranteed to be cleaned up. It also has a bunch of methods to make file based things easier like creating a file, etc.

Install it with “gem install file_sandbox”

Posted by jeremy Filed in

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