diff --git a/src/libvterm/t/run-test.pl b/src/libvterm/t/run-test.pl
new file mode 100644
index 0000000..4ef0f26
--- /dev/null
+++ b/src/libvterm/t/run-test.pl
@@ -0,0 +1,196 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use Getopt::Long;
+use IO::Handle;
+use IPC::Open2 qw( open2 );
+use POSIX qw( WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG );
+
+my $VALGRIND = 0;
+GetOptions(
+   'valgrind|v+' => \$VALGRIND,
+) or exit 1;
+
+my ( $hin, $hout, $hpid );
+{
+   local $ENV{LD_LIBRARY_PATH} = ".libs";
+   my @command = "t/.libs/harness";
+   unshift @command, "valgrind", "--quiet", "--error-exitcode=126" if $VALGRIND;
+
+   $hpid = open2 $hout, $hin, @command or die "Cannot open2 harness - $!";
+}
+
+my $exitcode = 0;
+
+my $command;
+my @expect;
+
+sub do_onetest
+{
+   $hin->print( "$command\n" );
+   undef $command;
+
+   my $fail_printed = 0;
+
+   while( my $outline = <$hout> ) {
+      last if $outline eq "DONE\n" or $outline eq "?\n";
+
+      chomp $outline;
+
+      if( !@expect ) {
+         print "# Test failed\n" unless $fail_printed++;
+         print "#    expected nothing more\n" .
+               "#   Actual:   $outline\n";
+         next;
+      }
+
+      my $expectation = shift @expect;
+
+      next if $expectation eq $outline;
+
+      print "# Test failed\n" unless $fail_printed++;
+      print "#   Expected: $expectation\n" .
+            "#   Actual:   $outline\n";
+   }
+
+   if( @expect ) {
+      print "# Test failed\n" unless $fail_printed++;
+      print "#   Expected: $_\n" .
+            "#    didn't happen\n" for @expect;
+   }
+
+   $exitcode = 1 if $fail_printed;
+}
+
+sub do_line
+{
+   my ( $line ) = @_;
+
+   if( $line =~ m/^!(.*)/ ) {
+      do_onetest if defined $command;
+      print "> $1\n";
+   }
+
+   # Commands have capitals
+   elsif( $line =~ m/^([A-Z]+)/ ) {
+      # Some convenience formatting
+      if( $line =~ m/^(PUSH|ENCIN) (.*)$/ ) {
+         # we're evil
+         my $string = eval($2);
+         $line = "$1 " . unpack "H*", $string;
+      }
+
+      do_onetest if defined $command;
+
+      $command = $line;
+      undef @expect;
+   }
+   # Expectations have lowercase
+   elsif( $line =~ m/^([a-z]+)/ ) {
+      # Convenience formatting
+      if( $line =~ m/^(text|encout) (.*)$/ ) {
+         $line = "$1 " . join ",", map sprintf("%x", $_), eval($2);
+      }
+      elsif( $line =~ m/^(output) (.*)$/ ) {
+         $line = "$1 " . join ",", map sprintf("%x", $_), unpack "C*", eval($2);
+      }
+      elsif( $line =~ m/^control (.*)$/ ) {
+         $line = sprintf "control %02x", eval($1);
+      }
+      elsif( $line =~ m/^csi (\S+) (.*)$/ ) {
+         $line = sprintf "csi %02x %s", eval($1), $2; # TODO
+      }
+      elsif( $line =~ m/^(escape|osc|dcs) (.*)$/ ) {
+         $line = "$1 " . join "", map sprintf("%02x", $_), unpack "C*", eval($2);
+      }
+      elsif( $line =~ m/^putglyph (\S+) (.*)$/ ) {
+         $line = "putglyph " . join( ",", map sprintf("%x", $_), eval($1) ) . " $2";
+      }
+      elsif( $line =~ m/^(?:movecursor|scrollrect|moverect|erase|damage|sb_pushline|sb_popline|settermprop|setmousefunc) / ) {
+         # no conversion
+      }
+      else {
+         warn "Unrecognised test expectation '$line'\n";
+      }
+
+      push @expect, $line;
+   }
+   # ?screen_row assertion is emulated here
+   elsif( $line =~ s/^\?screen_row\s+(\d+)\s*=\s*// ) {
+      my $row = $1;
+      my $row1 = $row + 1;
+      my $want = eval($line);
+
+      do_onetest if defined $command;
+
+      # TODO: may not be 80
+      $hin->print( "\?screen_chars $row,0,$row1,80\n" );
+      my $response = <$hout>;
+      chomp $response;
+
+      $response = pack "C*", map hex, split m/,/, $response;
+      if( $response ne $want ) {
+         print "# Assert ?screen_row $row failed:\n" .
+               "# Expected: $want\n" .
+               "# Actual:   $response\n";
+         $exitcode = 1;
+      }
+   }
+   # Assertions start with '?'
+   elsif( $line =~ s/^\?([a-z]+.*?=)\s+// ) {
+      do_onetest if defined $command;
+
+      my ( $assertion ) = $1 =~ m/^(.*)\s+=/;
+
+      $hin->print( "\?$assertion\n" );
+      my $response = <$hout>; defined $response or wait, die "Test harness failed - $?\n";
+      chomp $response;
+
+      if( $response ne $line ) {
+         print "# Assert $assertion failed:\n" .
+               "# Expected: $line\n" .
+               "# Actual:   $response\n";
+         $exitcode = 1;
+      }
+   }
+   # Test controls start with '$'
+   elsif( $line =~ s/\$SEQ\s+(\d+)\s+(\d+):\s*// ) {
+      my ( $low, $high ) = ( $1, $2 );
+      foreach my $val ( $low .. $high ) {
+         ( my $inner = $line ) =~ s/\\#/$val/g;
+         do_line( $inner );
+      }
+   }
+   elsif( $line =~ s/\$REP\s+(\d+):\s*// ) {
+      my $count = $1;
+      do_line( $line ) for 1 .. $count;
+   }
+   else {
+      die "Unrecognised TEST line $line\n";
+   }
+}
+
+open my $test, "<", $ARGV[0] or die "Cannot open test script $ARGV[0] - $!";
+
+while( my $line = <$test> ) {
+   $line =~ s/^\s+//;
+   next if $line =~ m/^(?:#|$)/;
+
+   chomp $line;
+   do_line( $line );
+}
+
+do_onetest if defined $command;
+
+close $hin;
+close $hout;
+
+waitpid $hpid, 0;
+if( $? ) {
+   printf STDERR "Harness exited %d\n", WEXITSTATUS($?)   if WIFEXITED($?);
+   printf STDERR "Harness exit signal %d\n", WTERMSIG($?) if WIFSIGNALED($?);
+   $exitcode = WIFEXITED($?) ? WEXITSTATUS($?) : 125;
+}
+
+exit $exitcode;