RUBY-420 enforce lower bound on refresh interval

lib/mongo/repl_set_connection.rb

@@ -476,7 +476,10 @@ module Mongo
 
       # Refresh
       @refresh_mode = opts.fetch(:refresh_mode, false)
-      @refresh_interval = opts[:refresh_interval] || 90
+      @refresh_interval = opts.fetch(:refresh_interval, 90)
+      if @refresh_mode && @refresh_interval < 60
+        @refresh_interval = 60
+      end
 
       if @refresh_mode == :async
         warn ":async refresh mode has been deprecated. Refresh

test/unit/connection_test.rb

@@ -41,6 +41,12 @@ class ConnectionTest < Test::Unit::TestCase
       end
 
       context "given a replica set" do
+        should "enforce a minimum refresh_interval" do
+          @conn = ReplSetConnection.new(['localhost:27017'],
+            :connect => false, :refresh_mode => :sync, :refresh_interval => 10)
+          assert_equal 60, @conn.refresh_interval
+        end
+
         should "warn if invalid options are specified" do
           conn = ReplSetConnection.allocate
           opts = {:connect => false}