diff --git a/t/tokenization-external.t b/t/tokenization-external.t
new file mode 100644
index 0000000..e867aed
--- /dev/null
+++ b/t/tokenization-external.t
@@ -0,0 +1,51 @@
+use strict;
+use warnings;
+use Test::More;
+use File::Basename 'dirname';
+use Data::Dumper;
+use File::Spec::Functions qw/catfile/;
+use File::Temp 'tempfile';
+use Test::XML::Loy;
+
+use FindBin;
+BEGIN {
+  unshift @INC, "$FindBin::Bin/../lib";
+};
+
+require_ok('KorAP::XML::TEI::Tokenizer::External');
+
+my $f = dirname(__FILE__);
+my $cmd = catfile($f, 'cmd', 'tokenizer.pl');
+
+# Test aggressive
+my $ext = KorAP::XML::TEI::Tokenizer::External->new(
+  'perl ' . $cmd
+  #  'java -cp Ingestion/target/KorAP-Ingestion-pipeline.jar de.ids_mannheim.korap.tokenizer.KorAPTokenizerImpl'
+);
+
+$ext->tokenize("Der alte Mann");
+# TODO:
+#   see comments on $sep in 'lib/KorAP/XML/TEI/Tokenizer/External.pm'
+#$ext->tokenize("ging über die Straße");
+
+my $str = $ext->to_string('unknown');
+my $t = Test::XML::Loy->new($str);
+$t->attr_is('layer spanList span:nth-child(1)', 'to', 3);
+$t->attr_is('layer spanList span:nth-child(2)', 'from', 4);
+$t->attr_is('layer spanList span:nth-child(2)', 'to', 8);
+$t->attr_is('layer spanList span:nth-child(3)', 'from', 9);
+$t->attr_is('layer spanList span:nth-child(3)', 'to', 13);
+$t->element_count_is('layer spanList span', 3);
+
+$ext->reset;
+$ext->tokenize("Hu aha\ndas ist cool");
+
+$str = $ext->to_string('unknown');
+$t = Test::XML::Loy->new($str);
+$t->attr_is('layer spanList span:nth-child(1)', 'to', 2);
+$t->attr_is('layer spanList span:nth-child(2)', 'from', 3);
+$t->attr_is('layer spanList span:nth-child(2)', 'to', 6);
+$t->element_count_is('layer spanList span', 2);
+
+
+done_testing;