flexnbd: Make a test a bit stricter

tests/acceptance/test_write_during_migration.rb

@@ -35,22 +35,26 @@ class TestWriteDuringMigration < Test::Unit::TestCase
     end
   end
 
+  def debug_arg
+    ENV['DEBUG'] ? "--verbose" : ""
+  end
+
 
   def launch_servers
     @dst_proc = fork() {
-      cmd = "#{@flexnbd} listen -l 127.0.0.1 -p #{@dest_port} -f #{@dest_file} -s #{@dest_sock}"
+      cmd = "#{@flexnbd} listen -l 127.0.0.1 -p #{@dest_port} -f #{@dest_file} -s #{@dest_sock} #{debug_arg}"
       exec cmd
     }
 
     @src_proc = fork() {
-      cmd = "#{@flexnbd} serve -l 127.0.0.1 -p #{@source_port} -f #{@source_file} -s #{@source_sock}"
+      cmd = "#{@flexnbd} serve -l 127.0.0.1 -p #{@source_port} -f #{@source_file} -s #{@source_sock} #{debug_arg}"
       exec cmd
     }
     begin
       awaiting = nil
       Timeout.timeout(10) do
         awaiting = :source
-        sleep 0.1 while !File.exists?( @source_sock ) 
+        sleep 0.1 while !File.exists?( @source_sock )
         awaiting = :dest
         sleep 0.1 while !File.exists?( @dest_sock )
       end
@@ -79,7 +83,7 @@ class TestWriteDuringMigration < Test::Unit::TestCase
 
   def start_mirror
     UNIXSocket.open(@source_sock) {|sock|
-      sock.write(["mirror", "127.0.0.1", @dest_port.to_s, "unlink"].join("\x0A") + "\x0A\x0A")
+      sock.write(["mirror", "127.0.0.1", @dest_port.to_s, "exit"].join("\x0A") + "\x0A\x0A")
       sock.flush
       rsp = sock.readline
     }
@@ -101,14 +105,15 @@ class TestWriteDuringMigration < Test::Unit::TestCase
     Dir.mktmpdir() do |tmpdir|
       Dir.chdir( tmpdir ) do
         make_files()
-        
+
         launch_servers()
 
         src_writer = Thread.new do
           client = FlexNBD::FakeSource.new( "127.0.0.1", @source_port, "Timed out connecting" )
+          offsets = Range.new(0, (@size - @write_data.size) / 4096 ).to_a
           loop do
             begin
-              client.write(0, @write_data)
+              client.write(offsets[rand(offsets.size)] * 4096, @write_data)
             rescue => err
               # We expect a broken write at some point, so ignore it
               break
@@ -119,9 +124,25 @@ class TestWriteDuringMigration < Test::Unit::TestCase
         start_mirror()
         wait_for_quit()
         src_writer.join
+
+        # Ensure each block matches
+        File.open(@source_file, "r") do |source|
+          File.open(@dest_file, "r") do |dest|
+            0.upto( @size / 4096 ) do |block_num|
+              s_data = source.read( 4096 )
+              d_data = source.read( 4096 )
+
+              assert s_data == d_data, "Block #{block_num} mismatch!"
+
+              source.seek( 4096, IO::SEEK_CUR )
+              dest.seek( 4096, IO::SEEK_CUR )
+            end
+          end
+        end
       end
     end
   end
 
 
 end
+