Postgresql: add test case for setting custom libpq connection parameters

activerecord/test/cases/adapters/postgresql/connection_test.rb

@@ -2,6 +2,9 @@
 
 module ActiveRecord
   class PostgresqlConnectionTest < ActiveRecord::TestCase
+    class NonExistentTable < ActiveRecord::Base
+    end
+
     def setup
       super
       @connection = ActiveRecord::Base.connection
@@ -10,5 +13,17 @@ def setup
     def test_encoding
       assert_not_nil @connection.encoding
     end
+
+    # Ensure, we can set connection params using the example of Generic
+    # Query Optimizer (geqo). It is 'on' per default.
+    def test_connection_options
+      params = ActiveRecord::Base.connection_config.dup
+      params[:options] = "-c geqo=off"
+      NonExistentTable.establish_connection(params)
+
+      # Verify the connection param has been applied.
+      expect = NonExistentTable.connection.query('show geqo').first.first
+      assert_equal 'off', expect
+    end
   end
 end