#+TITLE: Testing Rails Components That Require Cache
#+DATE: 2023-04-28T00:14:14-04:00
#+DRAFT: false
#+DESCRIPTION: How to test rails components that require cache without caching everything
#+TAGS[]: ruby rails cache
#+KEYWORDS[]: ruby rails cache
#+SLUG:
#+SUMMARY:

If you're in the default testing environment your rails cache is
[[https://api.rubyonrails.org/classes/ActiveSupport/Cache/NullStore.html][=ActiveSupport::Cache::NullStore=]] which will always succeed but it
doesn't actually store or return anything.

There's an almost completely undocumented method called
=with_local_cache= on =NullStore= that lets you run a block with a
=MemoryStore= instead of a =NullStore= for the duration of the block.
This happens because it =prepends= the
[[https://api.rubyonrails.org/classes/ActiveSupport/Cache/Strategy/LocalCache.html][=ActiveSupport::Cache::Strategy::LocalCache=]] class. This lets you test
one or two things that require caching without enabling it on all
tests and slowing everything down.

#+begin_src ruby
   Rails.cache.class.name
   # => "ActiveSupport::Cache::NullStore"
   Rails.cache.write("a", 3)
   # => true
   Rails.cache.read("a")
   # => nil
   Rails.cache.with_local_cache do
     Rails.cache.write("a", 5)
     p Rails.cache.read("a")
   end
   5
   # => 5
#+end_src