3 files changed, 181 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index bab2a401eb..e99a4854ce 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -13,6 +13,7 @@ require 'active_support/testing/assertions'
 require 'active_support/testing/deprecation'
 require 'active_support/testing/declarative'
 require 'active_support/testing/pending'
+require 'active_support/testing/isolation'
 
 module ActiveSupport
   class TestCase < ::Test::Unit::TestCase
diff --git a/activesupport/lib/active_support/testing/isolation.rb b/activesupport/lib/active_support/testing/isolation.rb
new file mode 100644
index 0000000000..8b2957fbe1
--- /dev/null
+++ b/activesupport/lib/active_support/testing/isolation.rb
@@ -0,0 +1,39 @@
+module ActiveSupport::Testing
+  class ProxyTestResult
+    def initialize
+      @calls = []
+    end
+
+    def __replay__(result)
+      @calls.each do |name, args|
+        result.send(name, *args)
+      end
+    end
+
+    def method_missing(name, *args)
+      @calls << [name, args]
+    end
+  end
+
+  module Isolation
+    def run(result)
+      yield(Test::Unit::TestCase::STARTED, name)
+
+      read, write = IO.pipe
+
+      pid = fork do
+        # child
+        read.close
+        proxy = ProxyTestResult.new
+        super(proxy) { }
+        write.puts [Marshal.dump(proxy)].pack("m")
+        exit!
+      end
+
+      write.close
+      Marshal.load(read.read.unpack("m")[0]).__replay__(result)
+      Process.wait2(pid)
+      yield(Test::Unit::TestCase::FINISHED, name)
+    end
+  end
+end
+\ No newline at end of file
diff --git a/activesupport/test/isolation_test.rb b/activesupport/test/isolation_test.rb
new file mode 100644
index 0000000000..4adf49ff62
--- /dev/null
+++ b/activesupport/test/isolation_test.rb
@@ -0,0 +1,141 @@
+require 'abstract_unit'
+
+# Does awesome
+if ENV['CHILD']
+  class ChildIsolationTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+
+    def setup
+      @instance = "HELLO"
+    end
+
+    def teardown
+      raise if @boom
+    end
+
+    test "runs the test" do
+      assert true
+    end
+
+    test "captures errors" do
+      raise
+    end
+
+    test "captures failures" do
+      assert false
+    end
+
+    test "first runs in isolation" do
+      assert_nil $x
+      $x = 1
+    end
+
+    test "second runs in isolation" do
+      assert_nil $x
+      $x = 2
+    end
+
+    test "runs with slow tests" do
+      sleep 0.3
+      assert true
+      sleep 0.2
+    end
+
+    test "runs setup" do
+      assert "HELLO", @instance
+    end
+
+    test "runs teardown" do
+      @boom = true
+    end
+
+    test "resets requires one" do
+      assert !defined?(Racc)
+      require 'racc/parser'
+    end
+
+    test "resets requires two" do
+      assert !defined?(Racc)
+      require 'racc/parser'
+    end
+  end
+else
+  class ParentIsolationTest < ActiveSupport::TestCase
+
+    ENV["CHILD"] = "1"
+    OUTPUT = `#{Gem.ruby} -I#{File.dirname(__FILE__)} #{File.expand_path(__FILE__)} -v`
+    ENV.delete("CHILD")
+
+    def setup
+      # Extract the results
+      @results = {}
+      OUTPUT[/Started\n\s*(.*)\s*\nFinished/mi, 1].split(/\s*\n\s*/).each do |result|
+        result =~ %r'^(\w+)\(\w+\):\s*(\.|E|F)$'
+        @results[$1] = { 'E' => :error, '.' => :success, 'F' => :failure }[$2]
+      end
+
+      # Extract the backtraces
+      @backtraces = {}
+      OUTPUT.scan(/^\s*\d+\).*?\n\n/m).each do |backtrace|
+        # \n  1) Error:\ntest_captures_errors(ChildIsolationTest):
+        backtrace =~ %r'\s*\d+\)\s*(Error|Failure):\n(\w+)'i
+        @backtraces[$2] = { :type => $1, :output => backtrace }
+      end
+    end
+
+    def assert_failing(name)
+      assert_equal :failure, @results[name.to_s], "Test #{name} did not fail"
+    end
+
+    def assert_passing(name)
+      assert_equal :success, @results[name.to_s], "Test #{name} did not pass"
+    end
+
+    def assert_erroring(name)
+      assert_equal :error, @results[name.to_s], "Test #{name} did not error"
+    end
+
+    test "has all tests" do
+      assert_equal 10, @results.length
+    end
+
+    test "passing tests are still reported" do
+      assert_passing :test_runs_the_test
+      assert_passing :test_runs_with_slow_tests
+    end
+
+    test "resets global variables" do
+      assert_passing :test_first_runs_in_isolation
+      assert_passing :test_second_runs_in_isolation
+    end
+
+    test "resets requires" do
+      assert_passing :test_resets_requires_one
+      assert_passing :test_resets_requires_two
+    end
+
+    test "erroring tests are still reported" do
+      assert_erroring :test_captures_errors
+    end
+
+    test "runs setup and teardown methods" do
+      assert_passing :test_runs_setup
+      assert_erroring :test_runs_teardown
+    end
+
+    test "correct tests fail" do
+      assert_failing :test_captures_failures
+    end
+
+    test "backtrace is printed for errors" do
+      assert_equal 'Error', @backtraces["test_captures_errors"][:type]
+      assert_match %{isolation_test.rb:21:in `test_captures_errors'}, @backtraces["test_captures_errors"][:output]
+    end
+
+    test "backtrace is printed for failures" do
+      assert_equal 'Failure', @backtraces["test_captures_failures"][:type]
+      assert_match %{isolation_test.rb:25:in `test_captures_failures'}, @backtraces["test_captures_failures"][:output]
+    end
+
+  end
+end
+\ No newline at end of file