Share already loaded fixtures across test classes

`self.class` is a fairly narrow cache key, so it doesn't hit that much,
but more importantly, since nothing clears that cache, on large test
suites it keeps growing extremely large.

Using the list of fixtures as a cache key doesn't strictly solve
the growth issue, but most classes actually load all fixtures so
this should shrink the cache size considerably.

Author: byroot

activerecord/lib/active_record/test_fixtures.rb

@@ -79,7 +79,7 @@ def fixtures(*fixture_set_names)
           fixture_set_names = fixture_set_names.flatten.map(&:to_s)
         end
 
-        self.fixture_table_names |= fixture_set_names
+        self.fixture_table_names = (fixture_table_names | fixture_set_names).sort
         setup_fixture_accessors(fixture_set_names)
       end
 
@@ -131,17 +131,17 @@ def setup_fixtures(config = ActiveRecord::Base)
 
       @fixture_cache = {}
       @fixture_connections = []
+      @fixture_cache_key = [self.class.fixture_table_names.dup, self.class.fixture_paths.dup, self.class.fixture_class_names.dup]
       @@already_loaded_fixtures ||= {}
       @connection_subscriber = nil
       @saved_pool_configs = Hash.new { |hash, key| hash[key] = {} }
 
       # Load fixtures once and begin transaction.
       if run_in_transaction?
-        if @@already_loaded_fixtures[self.class]
-          @loaded_fixtures = @@already_loaded_fixtures[self.class]
-        else
-          @loaded_fixtures = load_fixtures(config)
-          @@already_loaded_fixtures[self.class] = @loaded_fixtures
+        @loaded_fixtures = @@already_loaded_fixtures[@fixture_cache_key]
+        unless @loaded_fixtures
+          @@already_loaded_fixtures.clear
+          @loaded_fixtures = @@already_loaded_fixtures[@fixture_cache_key] = load_fixtures(config)
         end
 
         # Begin transactions for connections already established
@@ -179,7 +179,7 @@ def setup_fixtures(config = ActiveRecord::Base)
       # Load fixtures for every test.
       else
         ActiveRecord::FixtureSet.reset_cache
-        @@already_loaded_fixtures[self.class] = nil
+        @@already_loaded_fixtures.clear
         @loaded_fixtures = load_fixtures(config)
       end
 

activerecord/test/cases/fixtures_test.rb

@@ -783,7 +783,7 @@ class MultipleFixturesTest < ActiveRecord::TestCase
   fixtures :developers, :accounts
 
   def test_fixture_table_names
-    assert_equal %w(topics developers accounts), fixture_table_names
+    assert_equal %w(accounts developers topics), fixture_table_names
   end
 end
 
@@ -815,7 +815,7 @@ class OverlappingFixturesTest < ActiveRecord::TestCase
   fixtures :developers, :accounts
 
   def test_fixture_table_names
-    assert_equal %w(topics developers accounts), fixture_table_names
+    assert_equal %w(accounts developers topics), fixture_table_names
   end
 end
 
@@ -1163,6 +1163,8 @@ def blank_teardown; end
   alias_method :teardown_fixtures, :blank_teardown
   alias_method :teardown, :blank_teardown
 
+  fixtures rand.to_s # bypass fixtures cache
+
   def test_no_rollback_in_teardown_unless_transaction_active
     assert_equal 0, ActiveRecord::Base.connection.open_transactions
     assert_raise(RuntimeError) { ar_setup_fixtures }

activerecord/test/cases/view_test.rb

@@ -101,6 +101,8 @@ def drop_view(name)
 
   class ViewWithoutPrimaryKeyTest < ActiveRecord::TestCase
     include SchemaDumpingHelper
+
+    self.use_transactional_tests = false
     fixtures :books
 
     class Paperback < ActiveRecord::Base; end