Fix leaky test

This test was changing the user of Person and affecting other tests.
We need to reset the user after the test has run.

Gemfile

@@ -15,6 +15,8 @@ gem "rubocop-packaging"
 gem "rubocop-performance"
 gem "rubocop-rails"
 
+gem "minitest-bisect"
+
 gemspec
 
 platform :mri do

test/cases/base_test.rb

@@ -306,6 +306,7 @@ def test_user_reader_uses_superclass_user_until_written
     # Superclass is Object so returns nil.
     assert_nil ActiveResource::Base.user
     assert_nil Class.new(ActiveResource::Base).user
+    person_user = Person.user
     Person.user = "anonymous".dup
 
     # Subclass uses superclass user.
@@ -338,6 +339,8 @@ def test_user_reader_uses_superclass_user_until_written
 
     fruit.user = "client"
     assert_equal fruit.user, apple.user, "subclass did not adopt changes from parent class"
+  ensure
+    Person.user = person_user
   end
 
   def test_password_reader_uses_superclass_password_until_written