added some more test cases

lib/net/snmp.rb

@@ -88,6 +88,7 @@ module Net
 	    @pdu_type = args[:pdu_type] # leave nil unless specified; there's no reasonable default value.
 	    @error_status = args[:error_status] || 0
 	    @error_index = args[:error_index] || 0
+	    @variables = args[:variables] || []
 	end
 
 	#--

tests/testsnmp.rb

@@ -75,6 +75,8 @@ class TestSnmp < Test::Unit::TestCase
 
   def test_malformations
       pdu = Net::SnmpPdu.new
+	pdu.version = 0
+	pdu.version = 2
       assert_raise( Net::SnmpPdu::Error ) {
 	pdu.version = 100
       }
@@ -102,6 +104,15 @@ class TestSnmp < Test::Unit::TestCase
       assert_equal( SnmpGetResponse,  pdu.to_ber_string )
   end
 
+  def test_make_bad_response
+      pdu = Net::SnmpPdu.new
+      assert_raise(Net::SnmpPdu::Error) {pdu.to_ber_string}
+      pdu.pdu_type = :get_response
+      pdu.request_id = 999
+      pdu.to_ber_string
+      # Not specifying variables doesn't create an error. (Maybe it should?)
+  end
+
 end