use `assert_not` instead of `refute` as mentioned in our guides.

As described in the "Follow Coding Conventions" section in our
contribution guide (http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#follow-the-coding-conventions)
we favor `assert_not` over `refute`.

While we don't usually make stylistic changes on it's own I opted to do
it in this case. The reason being that test cases are usually copied as
a starting point for new tests. This results in a spread of `refute` in
files that have been using it already.

1 files changed, 2 insertions, 2 deletions

diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 73cde05504..e7a269c695 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -91,7 +91,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    refute account.valid?
+    assert_not account.valid?
     assert_equal [{error: :blank}], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
@@ -108,7 +108,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    refute account.valid?
+    assert_not account.valid?
     assert_equal [{error: :blank}], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value