Exit with error when one appraisal fails

features/appraisals.feature

@@ -28,6 +28,11 @@ Feature: run a rake task through several appraisals
       require 'factory_girl'
       puts "Loaded #{Factory::VERSION}"
     end
+    task :fail do
+      require 'factory_girl'
+      puts "Fail #{Factory::VERSION}"
+      raise
+    end
     task :default => :version
     """
     When I successfully run "rake appraisal:install --trace"
@@ -55,3 +60,16 @@ Feature: run a rake task through several appraisals
     Then the output should contain "Loaded 1.3.0"
     And the output should contain "Loaded 1.3.2"
 
+  @disable-bundler
+  Scenario: run a failing task with one appraisal
+    When I run "rake appraisal:1.3.0 fail --trace"
+    Then the output should contain "Fail 1.3.0"
+    And the exit status should be 1
+
+  @disable-bundler
+  Scenario: run a failing task with all appraisals
+    When I run "rake appraisal fail --trace"
+    Then the output should contain "Fail 1.3.2"
+    But the output should not contain "Fail 1.3.0"
+    And the exit status should be 1
+

lib/appraisal/command.rb

@@ -16,7 +16,11 @@ def initialize(command, gemfile = nil)
 
     def run
       announce
-      with_clean_env { Kernel.system(@command) }
+      with_clean_env do
+        unless Kernel.system(@command)
+          exit(1)
+        end
+      end
     end
 
     def exec