Test that an invalid write gets an error response

tests/fakes/source/write_out_of_range.rb

@@ -0,0 +1,21 @@
+#!/usr/bin/env ruby
+# encoding: utf-8
+
+# Connect, read the hello then make a write request with an impossible
+# (from,len) pair.  We expect an error response, and not to be
+# disconnected.
+
+require 'flexnbd/fake_source'
+include FlexNBD::FakeSource
+
+addr, port = *ARGV
+client_sock = connect( addr, port, "Timed out connecting" )
+read_hello( client_sock )
+write_write_request( client_sock, 1 << 31, 1 << 31, "myhandle" )
+response = read_response( client_sock )
+
+fail "Not an error" if response[:error] == 0
+fail "Wrong handle" unless "myhandle" == response[:handle]
+
+client_sock.close
+exit(0)