Improve support for text siglen including underscore

Change-Id: I86204f2aae32834e1592335dca83f40cbf46f559
diff --git a/t/meta_artificial.t b/t/meta_artificial.t
index e6c3d10..6cd33cc 100644
--- a/t/meta_artificial.t
+++ b/t/meta_artificial.t
@@ -28,8 +28,8 @@
 # Metdata
 is($meta->{T_title}, 'Artificial Title', 'title');
 is($meta->{T_sub_title}, 'Artificial Subtitle', 'subTitle');
-is($doc->text_sigle, 'ART/ABC/00001', 'ID');
-is($doc->corpus_sigle, 'ART', 'corpusID');
+is($doc->text_sigle, 'A_RT/ABC/00001', 'ID');
+is($doc->corpus_sigle, 'A_RT', 'corpusID');
 is($meta->{D_pub_date}, '20010402', 'pubDate');
 is($meta->{S_pub_place}, 'Mannheim', 'pubPlace');
 is($meta->{S_pub_place_key}, 'DE', 'pubPlace key');