use flexmock for now

since we're not moving away from flexmock just yet, I updated my tests to use
flexmock to be consistent. cc @mtodd

Author: Jerry Cheung

test/test_helper.rb

@@ -2,7 +2,6 @@
 require 'test/unit'
 require 'net/ldap'
 require 'flexmock/test_unit'
-require 'minitest/mock'
 
 # Whether integration tests should be run.
 INTEGRATION = ENV.fetch("INTEGRATION", "skip") != "skip"

test/test_ldap_connection.rb

@@ -44,15 +44,15 @@ def test_modify_ops_replace
   end
 
   def test_write
-    mock = Minitest::Mock.new
-    mock.expect(:write, true, [[1.to_ber, "request"].to_ber_sequence])
+    mock = flexmock("socket")
+    mock.should_receive(:write).with([1.to_ber, "request"].to_ber_sequence).and_return(true)
     conn = Net::LDAP::Connection.new(:socket => mock)
     conn.send(:write, "request")
   end
 
   def test_write_with_controls
-    mock = Minitest::Mock.new
-    mock.expect(:write, true, [[1.to_ber, "request", "controls"].to_ber_sequence])
+    mock = flexmock("socket")
+    mock.should_receive(:write).with([1.to_ber, "request", "controls"].to_ber_sequence).and_return(true)
     conn = Net::LDAP::Connection.new(:socket => mock)
     conn.send(:write, "request", "controls")
   end