diff --git a/src/.cvsignore b/src/.cvsignore
index d6cbd59..3f24136 100644
--- a/src/.cvsignore
+++ b/src/.cvsignore
@@ -3,3 +3,4 @@ Makefile
 Makefile.in
 mbsync
 mdconvert
+tmp
diff --git a/src/run-tests.pl b/src/run-tests.pl
new file mode 100755
index 0000000..0e84b4a
--- /dev/null
+++ b/src/run-tests.pl
@@ -0,0 +1,375 @@
+#! /usr/bin/perl -w
+
+use strict;
+use File::Path;
+
+-d "tmp" or mkdir "tmp";
+chdir "tmp" or die "Cannot enter temp direcory.\n";
+
+sub show($$@);
+sub test($$);
+
+################################################################################
+
+my @x01 = (
+ [ 8,
+   1, 1, "F", 2, 2, "", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "F", 7, 7, "FT", 9, 0, "" ],
+ [ 8,
+   1, 1, "", 2, 2, "F", 3, 3, "F", 4, 4, "", 5, 5, "", 7, 7, "", 8, 8, "", 10, 0, "" ],
+ [ 8, 0, 0,
+   1, 1, "", 2, 2, "", 3, 3, "", 4, 4, "", 5, 5, "", 6, 6, "", 7, 7, "", 8, 8, "" ],
+);
+
+#show("01", "01", "", "", "");
+my @X01 = (
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "FT", 7, 7, "FT", 9, 9, "", 10, 10, "" ],
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 7, 7, "FT", 8, 8, "T", 9, 10, "", 10, 9, "" ],
+ [ 9, 0, 9,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 0, "", 7, 7, "FT", 0, 8, "", 10, 9, "", 9, 10, "" ],
+ [ "", "", "" ],
+);
+test(\@x01, \@X01);
+
+#show("01", "02", "", "", "Expunge Both\n");
+my @X02 = (
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 9, 9, "", 10, 10, "" ],
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 9, 10, "", 10, 9, "" ],
+ [ 9, 0, 9,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 10, 9, "", 9, 10, "" ],
+ [ "", "", "Expunge Both\n" ],
+);
+test(\@x01, \@X02);
+
+#show("01", "03", "", "", "Expunge Slave\n");
+my @X03 = (
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "FT", 7, 7, "FT", 9, 9, "", 10, 10, "" ],
+ [ 10,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 9, 10, "", 10, 9, "" ],
+ [ 9, 0, 9,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 0, "", 7, 7, "FT", 10, 9, "", 9, 10, "" ],
+ [ "", "", "Expunge Slave\n" ],
+);
+test(\@x01, \@X03);
+
+#show("01", "04", "", "", "Sync Pull\n");
+my @X04 = (
+ [ 9,
+   1, 1, "F", 2, 2, "", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "F", 7, 7, "FT", 9, 9, "" ],
+ [ 9,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 7, 7, "FT", 8, 8, "T", 9, 9, "", 10, 0, "" ],
+ [ 9, 0, 0,
+   1, 1, "F", 2, 2, "", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "", 7, 7, "FT", 0, 8, "", 9, 9, "" ],
+ [ "", "", "Sync Pull\n" ],
+);
+test(\@x01, \@X04);
+
+#show("01", "05", "", "", "Sync Flags\n");
+my @X05 = (
+ [ 8,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "F", 7, 7, "FT", 9, 0, "" ],
+ [ 8,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 7, 7, "FT", 8, 8, "", 10, 0, "" ],
+ [ 8, 0, 0,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "", 7, 7, "FT", 8, 8, "" ],
+ [ "", "", "Sync Flags\n" ],
+);
+test(\@x01, \@X05);
+
+#show("01", "06", "", "", "Sync Delete\n");
+my @X06 = (
+ [ 8,
+   1, 1, "F", 2, 2, "", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "FT", 7, 7, "FT", 9, 0, "" ],
+ [ 8,
+   1, 1, "", 2, 2, "F", 3, 3, "F", 4, 4, "", 5, 5, "", 7, 7, "", 8, 8, "T", 10, 0, "" ],
+ [ 8, 0, 0,
+   1, 1, "", 2, 2, "", 3, 3, "", 4, 4, "", 5, 5, "", 6, 0, "", 7, 7, "", 0, 8, "" ],
+ [ "", "", "Sync Delete\n" ],
+);
+test(\@x01, \@X06);
+
+#show("01", "07", "", "", "Sync New\n");
+my @X07 = (
+ [ 10,
+   1, 1, "F", 2, 2, "", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "F", 7, 7, "FT", 9, 9, "", 10, 10, "" ],
+ [ 10,
+   1, 1, "", 2, 2, "F", 3, 3, "F", 4, 4, "", 5, 5, "", 7, 7, "", 8, 8, "", 9, 10, "", 10, 9, "" ],
+ [ 9, 0, 9,
+   1, 1, "", 2, 2, "", 3, 3, "", 4, 4, "", 5, 5, "", 6, 6, "", 7, 7, "", 8, 8, "", 10, 9, "", 9, 10, "" ],
+ [ "", "", "Sync New\n" ],
+);
+test(\@x01, \@X07);
+
+#show("01", "08", "", "", "Sync PushFlags PullDelete\n");
+my @X08 = (
+ [ 8,
+   1, 1, "F", 2, 2, "F", 3, 3, "FS", 4, 4, "", 5, 5, "T", 6, 6, "F", 7, 7, "FT", 9, 0, "" ],
+ [ 8,
+   1, 1, "", 2, 2, "F", 3, 3, "F", 4, 4, "", 5, 5, "", 7, 7, "", 8, 8, "T", 10, 0, "" ],
+ [ 8, 0, 0,
+   1, 1, "", 2, 2, "F", 3, 3, "F", 4, 4, "", 5, 5, "", 6, 6, "", 7, 7, "", 0, 8, "" ],
+ [ "", "", "Sync PushFlags PullDelete\n" ],
+);
+test(\@x01, \@X08);
+
+################################################################################
+
+chdir "..";
+rmdir "tmp";
+print "OK.\n";
+exit 0;
+
+
+sub fcfg(@)
+{
+	return join(" // ", map({ my $t = $_; chomp $t; $t =~ s/\n/ \/ /g; $t; } @_));
+}
+
+sub qm($)
+{
+	shift;
+	s/\\/\\\\/g;
+	s/\"/\\"/g;
+	s/\"/\\"/g;
+	s/\n/\\n/g;
+	return $_;
+}
+
+# $global, $master, $slave, $channel
+sub runsync($$$)
+{
+	open(FILE, ">", ".mbsyncrc") or
+		die "Cannot open .mbsyncrc.\n";
+	print FILE
+"MaildirStore master
+Path ./
+Inbox ./master
+".shift()."
+MaildirStore slave
+Path ./
+Inbox ./slave
+".shift()."
+Channel test
+Master :master:
+Slave :slave:
+SyncState *
+".shift();
+	close FILE;
+	system "../mbsync -q -c .mbsyncrc test";
+	unlink ".mbsyncrc";
+}
+
+# $path
+sub readbox($)
+{
+	my $bn = shift;
+
+	(-d $bn) or
+		die "No mailbox '$bn'.\n";
+	(-d $bn."/tmp" and -d $bn."/new" and -d $bn."/cur") or
+		die "Invalid mailbox '$bn'.\n";
+	open(FILE, "<", $bn."/.uidvalidity") or die "Cannot read UID validity of mailbox '$bn'.\n";
+	my $dummy = <FILE>;
+	chomp(my $mu = <FILE>);
+	close FILE;
+	my %ms = ();
+	for my $d ("cur", "new") {
+		opendir(DIR, $bn."/".$d) or next;
+		for my $f (grep(!/^\.\.?$/, readdir(DIR))) {
+			my ($uid, $flg, $num);
+			if ($f =~ /^\d+\.\d+_\d+\.[-[:alnum:]]+,U=(\d+):2,(.*)$/) {
+				($uid, $flg) = ($1, $2);
+			} elsif ($f =~ /^\d+\.\d+_(\d+)\.[-[:alnum:]]+:2,(.*)$/) {
+				($uid, $flg) = (0, $2);
+			} else {
+				print STDERR "unrecognided file name '$f' in '$bn'.\n";
+				exit 1;
+			}
+			open(FILE, "<", $bn."/".$d."/".$f) or die "Cannot read message '$f' in '$bn'.\n";
+			while (<FILE>) {
+				/^Subject: (\d+)$/ && ($num = $1);
+			}
+			close FILE;
+			if (!defined($num)) {
+				print STDERR "message '$f' in '$bn' has no identifier.\n";
+				exit 1;
+			}
+			@{ $ms{$num} } = ($uid, $flg);
+		}
+	}
+	return ($mu, %ms);
+}
+
+# $boxname, $maxuid, @msgs
+sub mkbox($$@)
+{
+	my ($bn, $mu, @ms) = @_;
+
+	rmtree($bn);
+	(mkdir($bn) and mkdir($bn."/tmp") and mkdir($bn."/new") and mkdir($bn."/cur")) or
+		die "Cannot create mailbox $bn.\n";
+	open(FILE, ">", $bn."/.uidvalidity") or die "Cannot create UID validity for mailbox $bn.\n";
+	print FILE "1\n$mu\n";
+	close FILE;
+	while (@ms) {
+		my ($num, $uid, $flg) = (shift @ms, shift @ms, shift @ms);
+		if ($uid) {
+			$uid = ",U=".$uid;
+		} else {
+			$uid = "";
+		}
+		open(FILE, ">", $bn."/cur/0.1_".$num.".local".$uid.":2,".$flg) or
+			die "Cannot create message $num in mailbox $bn.\n";
+		print FILE "From: foo\nTo: bar\nDate: Thu, 1 Jan 1970 00:00:00 +0000\nSubject: $num\n\n";
+		close FILE;
+	}
+}
+
+# \@master, \@slave, @syncstate
+sub mkchan($$@)
+{
+	my ($m, $s, @t) = @_;
+	&mkbox("master", @{ $m });
+	&mkbox("slave", @{ $s });
+	open(FILE, ">", "slave/.mbsyncstate") or
+		die "Cannot create sync state.\n";
+	print FILE "1:".shift(@t)." 1:".shift(@t).":".shift(@t)."\n";
+	while (@t) {
+		print FILE shift(@t)." ".shift(@t)." ".shift(@t)."\n";
+	}
+	close FILE;
+}
+
+# $config, $boxname, $maxuid, @msgs
+sub ckbox($$$@)
+{
+	my ($cfg, $bn, $MU, @MS) = @_;
+
+	my ($mu, %ms) = readbox($bn);
+	if ($mu != $MU) {
+		print STDERR "NEXTUID mismatch for $bn - expected $MU, got $mu, config: $cfg\n";
+		exit 1;
+	}
+	while (@MS) {
+		my ($num, $uid, $flg) = (shift @MS, shift @MS, shift @MS);
+		if (!defined $ms{$num}) {
+			print STDERR "no message $bn:$num, config: $cfg\n";
+			exit 1;
+		}
+		if ($ms{$num}[0] ne $uid) {
+			print STDERR "UID mismatch for $bn:$num - expected $uid, got $ms{$num}[0], config: $cfg\n";
+			exit 1;
+		}
+		if ($ms{$num}[1] ne $flg) {
+			print STDERR "flag mismatch for $bn:$num - expected '$flg', got '$ms{$num}[1]', config: $cfg\n";
+			exit 1;
+		}
+	}
+}
+
+# $config, \@master, \@slave, @syncstate
+sub ckchan($$$@)
+{
+	my ($cfg, $M, $S, @T) = @_;
+	open(FILE, "<", "slave/.mbsyncstate") or
+		die "Cannot read sync state.\n";
+	my $l = <FILE>;
+	my @ls = <FILE>;
+	close FILE;
+	my $xl = "1:".shift(@T)." 1:".shift(@T).":".shift(@T)."\n";
+	if ($l ne $xl) {
+		print STDERR "Sync state header mismatch.
+Expected: $xl"."Got:      $l"."Config:   $cfg
+";
+		exit 1;
+	}
+	for $l (@ls) {
+		$xl = shift(@T)." ".shift(@T)." ".shift(@T)."\n";
+		if ($l ne $xl) {
+			print STDERR "Sync state entry mismatch.
+Expected: $xl"."Got:      $l"."Config:   $cfg
+";
+			exit 1;
+		}
+	}
+	&ckbox($cfg, "master", @{ $M });
+	&ckbox($cfg, "slave", @{ $S });
+}
+
+sub test($$)
+{
+	my ($sx, $tx) = @_;
+	mkchan($$sx[0], $$sx[1], @{ $$sx[2] });
+	&runsync(@{ $$tx[3] });
+	ckchan(fcfg(@{ $$tx[3] }), $$tx[0], $$tx[1], @{ $$tx[2] });
+	rmtree "slave";
+	rmtree "master";
+}
+
+# $id, $boxname
+sub showbox($$)
+{
+	my ($bn) = @_;
+
+	my ($mu, %ms) = readbox($bn);
+	my $frst = 1;
+	for my $num (sort {$a <=> $b} keys %ms) {
+		if ($frst) {
+			print " [ $mu,\n   ";
+			$frst = 0;
+		} else {
+			print ", ";
+		}
+		print "$num, $ms{$num}[0], \"$ms{$num}[1]\"";
+	}
+	print " ],\n";
+}
+
+# $num
+sub showchan()
+{
+	&showbox("master");
+	&showbox("slave");
+	open(FILE, "<", "slave/.mbsyncstate") or
+		die "Cannot read sync state.\n";
+	$_ = <FILE>;
+	/^1:(\d+) 1:(\d+):(\d+)\n$/;
+	my ($mxm, $mms, $mxs) = ($1, $2, $3);
+	my $frst = 1;
+	for (<FILE>) {
+		/^(\d+) (\d+) (.*)\n$/;
+		my ($mu, $su, $flg) = ($1, $2, $3);
+		if ($frst) {
+			print " [ $mxm, $mms, $mxs,\n   ";
+			$frst = 0;
+		} else {
+			print ", ";
+		}
+		print "$mu, $su, \"$flg\"";
+	}
+	print " ],\n";
+	close FILE;
+}
+
+sub show($$@)
+{
+	my ($sx, $tx, @sfx) = @_;
+	my @sp;
+	eval "\@sp = \@x$sx";
+	mkchan($sp[0], $sp[1], @{ $sp[2] });
+	print "my \@x$sx = (\n";
+	showchan();
+	print ");\n";
+	&runsync(@sfx);
+	print "my \@X$tx = (\n";
+	showchan();
+	print " [ ".join(", ", map('"'.qm($_).'"', @sfx))." ],\n";
+	print ");\n";
+	print "test(\\\@x$sx, \\\@X$tx);\n\n";
+	rmtree "slave";
+	rmtree "master";
+}