Clarify intent in the cache expansion tests

CHANGELOG.md

@@ -12,7 +12,7 @@ Fixes:
 
 Misc:
 
-- [#1878](https://github.com/rails-api/active_model_serializers/pull/1878) Cache key generation for serializers now uses `ActiveSupport::Cache.expand_cache_key` instead of `Enumerable#join` by default and is also overridable. This change should be backward-compatible. (@markiz)
+- [#1878](https://github.com/rails-api/active_model_serializers/pull/1878) Cache key generation for serializers now uses `ActiveSupport::Cache.expand_cache_key` instead of `Array#join` by default and is also overridable. This change should be backward-compatible. (@markiz)
 
 ### [v0.10.2 (2016-07-05)](https://github.com/rails-api/active_model_serializers/compare/v0.10.1...v0.10.2)
 

test/cache_test.rb

@@ -4,7 +4,8 @@
 
 module ActiveModelSerializers
   class CacheTest < ActiveSupport::TestCase
-    class AuthorWithCustomCacheKey < Author
+    class AuthorWithExpandableCacheElements < Author
+      # simply returns object's method as the cache key
       class DerivedCacheKey
         def initialize(object, method)
           @object = object
@@ -16,6 +17,8 @@ def cache_key
         end
       end
 
+      # instead of a primitive cache key returns a list of objects
+      # that require to be expanded themselves
       def cache_key
         [
           DerivedCacheKey.new(self, :name),
@@ -126,10 +129,10 @@ def test_cache_key_interpolation_with_updated_at_when_cache_key_is_not_defined_o
       assert_equal(uncached_author_serializer.attributes.to_json, cache_store.fetch(key).to_json)
     end
 
-    def test_cache_key_with_non_primitive_values
-      author = AuthorWithCustomCacheKey.new(id: 10, name: 'hello')
-      same_author = AuthorWithCustomCacheKey.new(id: 10, name: 'hello')
-      diff_author = AuthorWithCustomCacheKey.new(id: 11, name: 'hello')
+    def test_cache_key_expansion
+      author = AuthorWithExpandableCacheElements.new(id: 10, name: 'hello')
+      same_author = AuthorWithExpandableCacheElements.new(id: 10, name: 'hello')
+      diff_author = AuthorWithExpandableCacheElements.new(id: 11, name: 'hello')
 
       author_serializer = AuthorSerializer.new(author)
       same_author_serializer = AuthorSerializer.new(same_author)