1 files changed, 10 insertions, 0 deletions
diff --git a/Library/Homebrew/test/testing_env.rb b/Library/Homebrew/test/testing_env.rb
index 6be622cc5..214aa9789 100644
--- a/Library/Homebrew/test/testing_env.rb
+++ b/Library/Homebrew/test/testing_env.rb
@@ -120,5 +120,15 @@ module Homebrew
     def bundle_path(name)
       Pathname.new("#{TEST_DIRECTORY}/mach/#{name}.bundle")
     end
+
+    def with_environment(partial_env)
+      old = ENV.to_hash
+      ENV.update partial_env
+      begin
+        yield
+      ensure
+        ENV.replace old
+      end
+    end
   end
 end