The at_exit hook to quit the selenium browser should not execute for unrelated child processes

lib/capybara/selenium/driver.rb

@@ -13,8 +13,10 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
   def browser
     unless @browser
       @browser = Selenium::WebDriver.for(options[:browser], options.reject { |key,val| SPECIAL_OPTIONS.include?(key) })
+
+      main = Process.pid
       at_exit do
-        @browser.quit
+        quit if Process.pid == main
       end
     end
     @browser
@@ -110,6 +112,12 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
     browser.switch_to.window(handle, &blk)
   end
 
+  def quit
+    @browser.quit
+  rescue Errno::ECONNREFUSED
+    # Browser must have already gone
+  end
+
 private
 
   def load_wait_for_ajax_support

spec/driver/selenium_driver_spec.rb

@@ -12,4 +12,15 @@ describe Capybara::Selenium::Driver do
   it_should_behave_like "driver with support for window switching"
   it_should_behave_like "driver without status code support"
   it_should_behave_like "driver with cookies support"
+
+  it "should not interfere with forking child processes" do
+    # Launch a browser, which registers the at_exit hook
+    browser = Capybara::Selenium::Driver.new(TestApp).browser
+
+    # Fork an unrelated child process. This should not run the code in the at_exit hook.
+    pid = fork { "child" }
+    Process.wait2(pid)[1].exitstatus.should == 0
+
+    browser.quit
+  end
 end