testing_env: extract with_environment to helper module

Library/Homebrew/test/helper/env.rb

@@ -0,0 +1,15 @@
+module Test
+  module Helper
+    module Env
+      def with_environment(partial_env)
+        old = ENV.to_hash
+        ENV.update partial_env
+        begin
+          yield
+        ensure
+          ENV.replace old
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/testing_env.rb

@@ -63,7 +63,9 @@ module Homebrew
   end
 
   class TestCase < ::Minitest::Test
+    require "test/helper/env"
     require "test/helper/shutup"
+    include Test::Helper::Env
     include Test::Helper::Shutup
 
     include VersionAssertions
@@ -112,16 +114,6 @@ module Homebrew
       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
-
     # Use a stubbed {Formulary::FormulaLoader} to make a given formula be found
     # when loading from {Formulary} with `ref`.
     def stub_formula_loader(formula, ref = formula.full_name)