Use rspec-retry to retry this test up to 3 times. (#977)

Looks like even a 2 second time delta is not always sufficient,
thus instead of always accepting a huge delta insist on a small delta
but run the test several times until it succeeds.

Author: p-mongo

Gemfile

@@ -25,6 +25,10 @@ group :development, :testing do
   end
 end
 
+group :testing do
+  gem 'rspec-retry'
+end
+
 group :development do
   gem 'ruby-prof', :platforms => :mri
   gem 'pry-rescue'

spec/mongo/client_spec.rb

@@ -1604,8 +1604,8 @@
         expect(session).to be_a(Mongo::Session)
       end
 
-      it 'sets the last use field to the current time' do
-        expect(session.instance_variable_get(:@server_session).last_use).to be_within(2).of(Time.now)
+      it 'sets the last use field to the current time', retry: 4 do
+        expect(session.instance_variable_get(:@server_session).last_use).to be_within(1).of(Time.now)
       end
 
       context 'when options are provided' do

spec/spec_helper.rb

@@ -79,6 +79,7 @@
 require 'support/authorization'
 require 'support/primary_socket'
 require 'support/constraints'
+require 'rspec/retry'
 
 RSpec.configure do |config|
   config.include(Authorization)