How do I inherit abstract unit tests in Ruby?

Question

I have two unit tests that should share a lot of common tests with slightly different setup methods. If I write something like

class Abstract < Test::Unit::TestCase
  def setup
    @field = create
  end

  def test_1
    ...
  end
end

class Concrete1 < Abstract
  def create
    SomeClass1.new
  end
end

class Concrete2 < Abstract
  def create
    SomeClass2.new
  end
end

then Concrete1 does not seem to inherit the tests from Abstract. Or at least I cannot get them to run in eclipse. If I choose "Run all TestCases" for the file that contains Concrete1 then Abstract is run even though I do not want it to be. If I specify Concrete1 then it does not run any tests at all! If I specify test_1 in Concrete1 then it complains it cannot find it ("uncaught throw :invalid_test (ArgumentError)").

I'm new to Ruby. What am I missing here?

Answer 1

The issue is that, as far as I can tell, Test::Unit keeps track of which classes inherit from Test::Unit::TestCase, and as a result, will only run tests from classes that directly inherit from it.

The way to work around this is to create a module with the tests you want, and then include that module in the classes that derive from Test::Unit::TestCase.

require 'test/unit'

module TestsToInclude
  def test_name
    assert(self.class.name.start_with?("Concrete"))
  end
end

class Concrete1 < Test::Unit::TestCase
  include TestsToInclude

  def test_something_bad
    assert(false)
  end
end

class Concrete2 < Test::Unit::TestCase
  include TestsToInclude

  def test_something_good
    assert(true)
  end
end

Output:

Loaded suite a
Started
.F..
Finished in 0.027873 seconds.

  1) Failure:
test_something_bad(Concrete1) [a.rb:13]:
<false> is not true.

4 tests, 4 assertions, 1 failures, 0 errors

shell returned 1