Add support for using an ARCONFIG environment variable to specify the…

… location of the config.yml file for running the tests

activerecord/RUNNING_UNIT_TESTS

@@ -9,17 +9,31 @@ You can build postgres and mysql databases using the build_postgresql and build_
 
 You can run a particular test file from the command line, e.g.
 
-  $ ruby test/cases/base_test.rb
+  $ ruby -Itest test/cases/base_test.rb
 
 To run a specific test:
 
-  $ ruby test/cases/base_test.rb -n test_something_works
+  $ ruby -Itest test/cases/base_test.rb -n test_something_works
 
 You can run with a database other than the default you set in test/config.yml, using the ARCONN
 environment variable:
 
-  $ ARCONN=postgresql ruby test/cases/base_test.rb
+  $ ARCONN=postgresql ruby -Itest test/cases/base_test.rb
 
 You can run all the tests for a given database via rake:
 
-  $ rake test_postgresql
+  $ rake test_mysql
+
+The 'rake test' task will run all the tests for mysql, mysql2, sqlite3 and postgresql.
+
+== Identity Map
+
+By default the tests run with the Identity Map turned off. But all tests should pass whether or
+not the identity map is on or off. You can turn it on using the IM env variable:
+
+  $ IM=true ruby -Itest test/case/base_test.rb
+
+== Config file
+
+By default, the config file is expected to be at the path test/config.yml. You can specify a
+custom location with the ARCONFIG environment variable.

activerecord/test/support/config.rb

@@ -10,13 +10,16 @@ def config
 
     private
 
+    def config_file
+      Pathname.new(ENV['ARCONFIG'] || TEST_ROOT + '/config.yml')
+    end
+
     def read_config
-      unless File.exist?(TEST_ROOT + '/config.yml')
-        FileUtils.cp TEST_ROOT + '/config.example.yml', TEST_ROOT + '/config.yml'
+      unless config_file.exist?
+        FileUtils.cp TEST_ROOT + '/config.example.yml', config_file
       end
 
-      raw = File.read(TEST_ROOT + '/config.yml')
-      erb = Erubis::Eruby.new(raw)
+      erb = Erubis::Eruby.new(config_file.read)
       expand_config(YAML.parse(erb.result(binding)).transform)
     end