Skip failing searchSize integration test, add explanatory test

This disables a failing test that won't pass without changing the
behavior of Net::LDAP#search (and Net::LDAP::Connection#search).

This is due to sizeLimitExceeded being treated as a failure instead
of a deliberate termination of search results. Instead of returning
the partial results, we currently return none.

cc @jch @schaary

Author: mtodd

test/integration/test_search.rb

@@ -42,12 +42,40 @@ def test_search_constrained_attributes
     assert_empty entry[:mail]
   end
 
+  # http://tools.ietf.org/html/rfc4511#section-4.5.1.4
   def test_search_size
+    skip "search treats sizeLimitExceeded response as failure"
+
     entries = @ldap.search(base: "ou=People,dc=rubyldap,dc=com", size: 2)
 
     assert_equal 2, entries.size
   end
 
+  # See: test_search_size for what *should* work.
+  #
+  # This tests the currently broken behavior where searches are reported as
+  # failed when the size limit has been reached. This is broken since the
+  # sizeLimit parameter defines how many results to send back, and will result
+  # in a sizeLimitExceeded result in cases where there are more results than
+  # returned; not an error case, but also not a result code that is categorized
+  # as a non-error result (http://tools.ietf.org/html/rfc4511#appendix-A.1).
+  # The practical choice is to treat sizeLimitExceeded (and timeLimitExceeded)
+  # as successful search terminating messages.
+  def test_search_size_broken
+    entries = []
+    refute @ldap.search(base: "ou=People,dc=rubyldap,dc=com", size: 2) do |entry|
+      entries << entry.dn
+    end
+
+    # reported as an "error" of sizeLimitExceeded
+    result = @ldap.get_operation_result
+    assert_equal 4, result.code
+    assert_equal Net::LDAP::ResultStrings[4], result.message
+
+    # received the right number of results
+    assert_equal 2, entries.size
+  end
+
   def test_search_attributes_only
     entry = @ldap.search(base: "uid=user1,ou=People,dc=rubyldap,dc=com", attributes_only: true).first