Test the source handles a dest crash after write correctly

tests/acceptance/fakes/dest/close_after_write.rb

@@ -0,0 +1,24 @@
+#!/usr/bin/env ruby
+
+# Wait for a sender connection, send a correct hello, wait for a write
+# request, then disconnect.  Simulate a server which crashes after
+# receiving the write, and before it can send a reply.  We then reopen
+# the server socket to check that the sender retries: since the
+# command-line has gone away, and can't feed an error back to the
+# user, we have to keep trying.
+
+require 'flexnbd/fake_dest'
+include FlexNBD
+
+server = FakeDest.new( *ARGV )
+client = server.accept( "Timed out waiting for a connection" )
+client.write_hello
+client.read_request
+client.close
+
+new_client = server.accept( "Timed out waiting for a reconnection" )
+new_client.close
+
+server.close
+
+exit 0

tests/acceptance/test_source_error_handling.rb

@@ -82,6 +82,13 @@ class TestSourceErrorHandling < Test::Unit::TestCase
   end
 
 
+  def test_disconnect_before_write_reply_causes_retry
+    run_fake( "dest/close_after_write" )
+    @env.mirror12_unchecked
+    assert_success
+  end
+
+
   private
   def run_fake(name)
     @env.run_fake( name, @env.ip, @env.port2 )