diff --git a/src/db/db/dbTestSupport.h b/src/db/db/dbTestSupport.h
index 365d7e602..f6dd94803 100644
--- a/src/db/db/dbTestSupport.h
+++ b/src/db/db/dbTestSupport.h
@@ -58,7 +58,7 @@ enum NormalizationMode
  *  @param tolerance A tolerance applied when comparing shapes in database units
  *  The layout is normalized by writing to a file and reading back
  */
-void compare_layouts (tl::TestBase *_this, const db::Layout &layout, const std::string &au_file, NormalizationMode norm = WriteGDS2, db::Coord tolerance = 0);
+void DB_PUBLIC compare_layouts (tl::TestBase *_this, const db::Layout &layout, const std::string &au_file, NormalizationMode norm = WriteGDS2, db::Coord tolerance = 0);
 
 /**
  *  @brief Compares a layout with a golden layout file with layer mapping
@@ -70,7 +70,7 @@ void compare_layouts (tl::TestBase *_this, const db::Layout &layout, const std::
  *  @param tolerance A tolerance applied when comparing shapes in database units
  *  The layout is normalized by writing to a file and reading back
  */
-void compare_layouts (tl::TestBase *_this, const db::Layout &layout, const std::string &au_file, const db::LayerMap &lmap, bool read_all_others, NormalizationMode norm = WriteGDS2, db::Coord tolerance = 0);
+void DB_PUBLIC compare_layouts (tl::TestBase *_this, const db::Layout &layout, const std::string &au_file, const db::LayerMap &lmap, bool read_all_others, NormalizationMode norm = WriteGDS2, db::Coord tolerance = 0);
 
 }
 
diff --git a/src/db/unit_tests/dbExpression.cc b/src/db/unit_tests/dbExpression.cc
new file mode 100644
index 000000000..9b43315fb
--- /dev/null
+++ b/src/db/unit_tests/dbExpression.cc
@@ -0,0 +1,214 @@
+
+/*
+
+  KLayout Layout Viewer
+  Copyright (C) 2006-2017 Matthias Koefferlein
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+
+#include "tlExpression.h"
+#include "tlUnitTest.h"
+#include "dbBox.h"
+#include "dbEdge.h"
+#include "dbLayout.h"
+#include "gsiDecl.h"
+#include "dbLayerProperties.h"
+#include "dbLayoutContextHandler.h"
+
+#include <stdlib.h>
+#include <math.h>
+
+// ref layout
+TEST(1)
+{
+  db::Layout l;
+  l.dbu (0.05);
+  l.insert_layer (db::LayerProperties (1, 15));
+  l.insert_layer (db::LayerProperties ("name"));
+  l.add_cell ("c1");
+  l.add_cell ("c2");
+
+  tl::Eval e, ee;
+  db::LayoutContextHandler ctx (&l);
+  e.set_ctx_handler (&ctx);
+  tl::Variant v;
+
+  bool error = false;
+
+  v = e.parse ("1um").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("20"));
+  v = e.parse ("1um2").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("400"));
+  v = e.parse ("1micron").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("20"));
+  v = e.parse ("1micron2").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("400"));
+  v = e.parse ("1mic").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("20"));
+  v = e.parse ("1mic2").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("400"));
+  v = e.parse ("1m").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("20000000"));
+  v = e.parse ("1m2/1e14").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("4"));
+  v = e.parse ("1mm").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("20000"));
+  v = e.parse ("1mm2").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("400000000"));
+  v = e.parse ("50nm").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("1"));
+  v = e.parse ("<1/15>").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("0"));
+  v = e.parse ("<   name >").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("1"));
+  v = e.parse ("<'n' + 'ame'>").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("1"));
+  v = e.parse ("<<c1>>").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("0"));
+  v = e.parse ("<<  c2   >>").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("1"));
+  v = e.parse ("<<'c' + '2'>>").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("1"));
+
+  error = true;
+  try {
+    v = e.parse ("60nm").execute (); // not a multiple of DBU
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+
+  error = true;
+  try {
+    v = ee.parse ("1 um").execute ();
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+
+  error = true;
+  try {
+    v = e.parse ("<1/1>").execute ();
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+
+  error = true;
+  try {
+    v = ee.parse ("<1/15>").execute ();
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+
+  error = true;
+  try {
+    v = ee.parse ("<<c1>>").execute ();
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+
+  error = true;
+  try {
+    v = e.parse ("<<c3>>").execute ();
+    error = false;
+  } catch (...) { }
+  EXPECT_EQ (error, true);
+}
+
+//  db objects as Variant payload
+TEST(10)
+{
+  tl::Variant v;
+  v = tl::Variant::make_variant (db::Box (db::Point (0, 10), db::Point (20, 30)));
+  EXPECT_EQ (v.is_user<db::Box> (), true)
+  EXPECT_EQ (v.to_parsable_string (), "[box:(0,10;20,30)]");
+
+  std::string s = v.to_parsable_string () + "," + tl::Variant (15.0).to_parsable_string ();
+  tl::Variant vv;
+  tl::Extractor ex (s.c_str ());
+  ex.read (vv);
+  ex.test (",");
+  ex.read (v);
+  EXPECT_EQ (vv.is_user<db::Box> (), true)
+  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
+  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
+  EXPECT_EQ (std::string(v.to_string()), "15");
+}
+
+//  db objects as Variant payload - backward compatibility check
+TEST(11)
+{
+  std::string s = "[box:(0,10;20,30)],##15";
+  tl::Variant vv;
+  tl::Variant v;
+  tl::Extractor ex (s.c_str ());
+  ex.read (vv);
+  ex.test (",");
+  ex.read (v);
+  EXPECT_EQ (vv.is_user<db::Box> (), true)
+  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
+  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
+  EXPECT_EQ (std::string(v.to_string()), "15");
+}
+
+//  db objects as Variant payload - backward compatibility check
+TEST(12)
+{
+  std::string s = "[Box:(0,10;20,30)],##15";
+  tl::Variant vv;
+  tl::Variant v;
+  tl::Extractor ex (s.c_str ());
+  ex.read (vv);
+  ex.test (",");
+  ex.read (v);
+  EXPECT_EQ (vv.is_user<db::Box> (), true)
+  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
+  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
+  EXPECT_EQ (std::string(v.to_string()), "15");
+}
+
+//  db objects as Variant payload - backward compatibility check
+TEST(13)
+{
+  std::string s = "[layer:1/0],##15";
+  tl::Variant vv;
+  tl::Variant v;
+  tl::Extractor ex (s.c_str ());
+  ex.read (vv);
+  ex.test (",");
+  ex.read (v);
+  EXPECT_EQ (vv.is_user<db::LayerProperties> (), true)
+  EXPECT_EQ (vv.to_parsable_string (), "[layer:1/0]");
+  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
+  EXPECT_EQ (std::string(v.to_string()), "15");
+}
+
+//  db objects as Variant payload - backward compatibility check
+TEST(14)
+{
+  std::string s = "[LayerInfo:1/0],##15";
+  tl::Variant vv;
+  tl::Variant v;
+  tl::Extractor ex (s.c_str ());
+  ex.read (vv);
+  ex.test (",");
+  ex.read (v);
+  EXPECT_EQ (vv.is_user<db::LayerProperties> (), true)
+  EXPECT_EQ (vv.to_parsable_string (), "[layer:1/0]");
+  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
+  EXPECT_EQ (std::string(v.to_string()), "15");
+}
+
diff --git a/src/db/unit_tests/unit_tests.pro b/src/db/unit_tests/unit_tests.pro
index 2baaf0d73..48df8e9a6 100644
--- a/src/db/unit_tests/unit_tests.pro
+++ b/src/db/unit_tests/unit_tests.pro
@@ -18,6 +18,7 @@ SOURCES = \
   dbCIFReader.cc \
   dbClip.cc \
   dbDXFReader.cc \
+  dbExpression.cc \
   dbEdge.cc \
   dbEdgePair.cc \
   dbEdgePairRelations.cc \
diff --git a/src/gsi/gsi.pro b/src/gsi/gsi.pro
index 6e190ecd3..b36a8d105 100644
--- a/src/gsi/gsi.pro
+++ b/src/gsi/gsi.pro
@@ -1,7 +1,7 @@
 
 TEMPLATE = subdirs
-SUBDIRS = gsi gsi_test unit_tests
+SUBDIRS = gsi unit_tests
 
 gsi_test.depends += gsi
-unit_tests.depends += gsi gsi_test
+unit_tests.depends += gsi
 
diff --git a/src/gsi/unit_tests/gsiExpression.cc b/src/gsi/unit_tests/gsiExpression.cc
index a1a36f2fe..464e487dd 100644
--- a/src/gsi/unit_tests/gsiExpression.cc
+++ b/src/gsi/unit_tests/gsiExpression.cc
@@ -24,8 +24,6 @@
 #include "gsiExpression.h"
 #include "gsiDecl.h"
 #include "gsiTest.h"
-#include "dbBox.h"
-#include "dbEdge.h"
 
 #include "tlUnitTest.h"
 
diff --git a/src/gsi/gsi_test/gsiTest.cc b/src/gsi/unit_tests/gsiTest.cc
similarity index 99%
rename from src/gsi/gsi_test/gsiTest.cc
rename to src/gsi/unit_tests/gsiTest.cc
index 8cfe1a603..a9b0f8e38 100644
--- a/src/gsi/gsi_test/gsiTest.cc
+++ b/src/gsi/unit_tests/gsiTest.cc
@@ -1050,7 +1050,8 @@ static gsi::Class<E> decl_e ("E",
   gsi::method ("x=", &E::set_x) +
   gsi::method ("x", &E::get_x) +
   gsi::method ("bindme", &E::bindme) +
-  gsi::method ("inst_count", &E::inst_count) 
+  gsi::method ("inst_count", &E::inst_count) +
+  gsi::method ("reset_inst", &E::reset_inst)
 );
 
 static gsi::Class<F> decl_f ("F",
diff --git a/src/gsi/gsi_test/gsiTest.h b/src/gsi/unit_tests/gsiTest.h
similarity index 100%
rename from src/gsi/gsi_test/gsiTest.h
rename to src/gsi/unit_tests/gsiTest.h
diff --git a/src/gsi/unit_tests/unit_tests.pro b/src/gsi/unit_tests/unit_tests.pro
index ef7b7770c..07f81a911 100644
--- a/src/gsi/unit_tests/unit_tests.pro
+++ b/src/gsi/unit_tests/unit_tests.pro
@@ -8,9 +8,13 @@ include($$PWD/../../lib_ut.pri)
 
 SOURCES = \
   gsiExpression.cc \
+  gsiTest.cc \
 
-INCLUDEPATH += $$TL_INC $$GSI_INC $$GSI_TEST_INC $$DB_INC
-DEPENDPATH += $$TL_INC $$GSI_INC $$GSI_TEST_INC $$DB_INC
+HEADERS += \
+  gsiTest.h \
 
-LIBS += -L$$DESTDIR_UT -lklayout_tl -lklayout_gsi -lgsi_test -lklayout_db
+INCLUDEPATH += $$TL_INC $$GSI_INC
+DEPENDPATH += $$TL_INC $$GSI_INC
+
+LIBS += -L$$DESTDIR_UT -lklayout_tl -lklayout_gsi
 
diff --git a/src/klayout.pri b/src/klayout.pri
index 0607d16a2..61e18a286 100644
--- a/src/klayout.pri
+++ b/src/klayout.pri
@@ -15,9 +15,6 @@ LAYBASIC_INC = $$PWD/laybasic/laybasic
 
 GSIQT_INC = $$PWD/gsiqt
 
-GSI_TEST_INC = $$PWD/gsi/gsi_test
-UT_INC = $$PWD/ut
-
 BD_INC = $$PWD/buddies/src/bd
 
 VERSION_INC = $$PWD/version
diff --git a/src/klayout.pro b/src/klayout.pro
index 9ef1f9a5d..2c4cbfff8 100644
--- a/src/klayout.pro
+++ b/src/klayout.pro
@@ -7,9 +7,7 @@ SUBDIRS = \
   klayout_main \
   unit_tests \
   tl \
-  gsi/gsi \
-  gsi/gsi_test \
-  gsi/unit_tests \
+  gsi \
   db \
   rdb \
   lym \
@@ -29,26 +27,25 @@ LANG_DEPENDS =
 equals(HAVE_RUBY, "1") {
   SUBDIRS += rba
   LANG_DEPENDS += rba
-  rba.depends += gsi/gsi gsi/gsi_test
+  rba.depends += gsi
 } else {
   SUBDIRS += rbastub
-  rbastub.depends += gsi/gsi
+  rbastub.depends += gsi
   LANG_DEPENDS += rbastub
 }
 
 equals(HAVE_PYTHON, "1") {
   SUBDIRS += pya
   LANG_DEPENDS += pya
-  pya-unit_tests.depends += gsi/gsi gsi/gsi_test
+  pya-unit_tests.depends += gsi
 } else {
   SUBDIRS += pyastub
-  pyastub.depends += gsi/gsi
+  pyastub.depends += gsi
   LANG_DEPENDS += pyastub
 }
 
-gsi-gsi.depends += tl
-gsi-gsi_test.depends += tl gsi/gsi
-db.depends += gsi/gsi
+gsi.depends += tl
+db.depends += gsi
 rdb.depends += db
 laybasic.depends += rdb
 ant.depends += laybasic
@@ -56,7 +53,7 @@ img.depends += laybasic
 edt.depends += laybasic
 drc.depends += rdb lym
 
-lym.depends += gsi/gsi $$LANG_DEPENDS
+lym.depends += gsi $$LANG_DEPENDS
 lay.depends += laybasic ant img edt lym
 ext.depends += lay
 lib.depends += db
@@ -64,13 +61,10 @@ buddies.depends += db
 
 equals(HAVE_QTBINDINGS, "1") {
   SUBDIRS += gsiqt
-  gsiqt.depends += gsi/gsi
+  gsiqt.depends += gsi
   laybasic.depends += gsiqt
 }
 
-# YES. It's gsi-unit_tests (for gsi/unit_tests)
-gsi-unit_tests.depends += gsi/gsi_test
-
 plugins.depends += lay ext lib
 
 klayout_main.depends += plugins drc
diff --git a/src/lym/unit_tests/unit_tests.pro b/src/lym/unit_tests/unit_tests.pro
index 01415fef6..9c62e03a9 100644
--- a/src/lym/unit_tests/unit_tests.pro
+++ b/src/lym/unit_tests/unit_tests.pro
@@ -9,8 +9,8 @@ include($$PWD/../../lib_ut.pri)
 SOURCES = \
   lymBasicTests.cc \
 
-INCLUDEPATH += $$LYM_INC $$TL_INC $$DB_INC $$GSI_INC
-DEPENDPATH += $$LYM_INC $$TL_INC $$DB_INC $$GSI_INC
+INCLUDEPATH += $$LYM_INC $$TL_INC $$GSI_INC
+DEPENDPATH += $$LYM_INC $$TL_INC $$GSI_INC
 
-LIBS += -L$$DESTDIR_UT -lklayout_lym -lklayout_tl -lklayout_db -lklayout_gsi
+LIBS += -L$$DESTDIR_UT -lklayout_lym -lklayout_tl -lklayout_gsi
 
diff --git a/src/pya/unit_tests/pya.cc b/src/pya/unit_tests/pya.cc
index 577d3546b..07a20f01c 100644
--- a/src/pya/unit_tests/pya.cc
+++ b/src/pya/unit_tests/pya.cc
@@ -24,7 +24,7 @@
 #ifdef HAVE_PYTHON
 
 #include "pya.h"
-#include "gsiTest.h"
+#include "gsiDecl.h"
 
 #include "tlUnitTest.h"
 
@@ -67,12 +67,12 @@ TEST (1)
   fn += "/testdata/python/basic.py";
   try {
     pya::PythonInterpreter::instance ()->load_file (fn.c_str ());
-    gsi_test::E::reset_inst ();
+    pya::PythonInterpreter::instance ()->eval_string ("pya.E.reset_inst()");
   } catch (tl::ExitException &ex) {
-    gsi_test::E::reset_inst ();
+    pya::PythonInterpreter::instance ()->eval_string ("pya.E.reset_inst()");
     EXPECT_EQ (ex.status (), 0);
   } catch (...) {
-    gsi_test::E::reset_inst ();
+    pya::PythonInterpreter::instance ()->eval_string ("pya.E.reset_inst()");
     throw;
   }
 }
diff --git a/src/pya/unit_tests/unit_tests.pro b/src/pya/unit_tests/unit_tests.pro
index cadfe9a40..d7c5d6c9d 100644
--- a/src/pya/unit_tests/unit_tests.pro
+++ b/src/pya/unit_tests/unit_tests.pro
@@ -9,8 +9,8 @@ include($$PWD/../../lib_ut.pri)
 SOURCES = \
   pya.cc
 
-INCLUDEPATH += $$GSI_TEST_INC $$PYA_INC $$DB_INC $$TL_INC $$GSI_INC
-DEPENDPATH += $$GSI_TEST_INC $$PYA_INC $$DB_INC $$TL_INC $$GSI_INC
+INCLUDEPATH += $$PYA_INC $$DB_INC $$TL_INC $$GSI_INC
+DEPENDPATH += $$PYA_INC $$DB_INC $$TL_INC $$GSI_INC
 
-LIBS += -L$$DESTDIR_UT -lgsi_test -lklayout_db -lklayout_tl -lklayout_gsi
+LIBS += -L$$DESTDIR_UT -lklayout_db -lklayout_tl -lklayout_gsi
 
diff --git a/src/rba/unit_tests/rba.cc b/src/rba/unit_tests/rba.cc
index fe7bf698c..b650cdab9 100644
--- a/src/rba/unit_tests/rba.cc
+++ b/src/rba/unit_tests/rba.cc
@@ -24,7 +24,7 @@
 #ifdef HAVE_RUBY
 
 #include "rba.h"
-#include "gsiTest.h"
+#include "gsiDecl.h"
 
 // On Windows, ruby.h is not compatible with windows.h which is included by utHead - at least not if 
 // windows.h is included before ruby.h ...
@@ -68,12 +68,12 @@ TEST (1)
   fn += "/testdata/ruby/basic.rb";
   try {
     rba::RubyInterpreter::instance ()->load_file (fn.c_str ());
-    gsi_test::E::reset_inst ();
+    rba::RubyInterpreter::instance ()->eval_string ("RBA::E.reset_inst");
   } catch (tl::ExitException &ex) {
-    gsi_test::E::reset_inst ();
+    rba::RubyInterpreter::instance ()->eval_string ("RBA::E.reset_inst");
     EXPECT_EQ (ex.status (), 0);
   } catch (...) {
-    gsi_test::E::reset_inst ();
+    rba::RubyInterpreter::instance ()->eval_string ("RBA::E.reset_inst");
     throw;
   }
 }
diff --git a/src/rba/unit_tests/unit_tests.pro b/src/rba/unit_tests/unit_tests.pro
index c17b48e53..bf63c9edd 100644
--- a/src/rba/unit_tests/unit_tests.pro
+++ b/src/rba/unit_tests/unit_tests.pro
@@ -9,8 +9,8 @@ include($$PWD/../../lib_ut.pri)
 SOURCES = \
   rba.cc
 
-INCLUDEPATH += $$GSI_TEST_INC $$RBA_INC $$TL_INC $$DB_INC $$GSI_INC
-DEPENDPATH += $$GSI_TEST_INC $$RBA_INC $$TL_INC $$DB_INC $$GSI_INC
+INCLUDEPATH += $$RBA_INC $$TL_INC $$DB_INC $$GSI_INC
+DEPENDPATH += $$RBA_INC $$TL_INC $$DB_INC $$GSI_INC
 
-LIBS += -L$$DESTDIR_UT -lgsi_test -lklayout_tl -lklayout_db -lklayout_gsi
+LIBS += -L$$DESTDIR_UT -lklayout_tl -lklayout_db -lklayout_gsi
 
diff --git a/src/tl/unit_tests/tlExpression.cc b/src/tl/unit_tests/tlExpression.cc
index 5da5401e4..855b1b4d0 100644
--- a/src/tl/unit_tests/tlExpression.cc
+++ b/src/tl/unit_tests/tlExpression.cc
@@ -24,10 +24,6 @@
 #include "tlExpression.h"
 #include "tlVariantUserClasses.h"
 #include "tlUnitTest.h"
-#include "dbBox.h"
-#include "dbEdge.h"
-#include "dbLayout.h"
-#include "dbLayoutContextHandler.h"
 
 #include <stdlib.h>
 #include <math.h>
@@ -317,6 +313,134 @@ TEST(1)
   EXPECT_EQ (v.to_string (), std::string ("aaaa"));
 }
 
+class Point
+{
+public:
+  Point () : m_x (0), m_y (0) { }
+
+  Point (int x, int y) : m_x (x), m_y (y) { }
+
+  int x () const { return m_x; }
+  int y () const { return m_y; }
+
+  std::string
+  to_string () const
+  {
+    return tl::db_to_string (m_x) + "," + tl::db_to_string (m_y);
+  }
+
+private:
+  int m_x, m_y;
+};
+
+class Box
+{
+public:
+  Box (int x1, int y1, int x2, int y2)
+    : m_p1 (x1 < x2 ? x1 : x2, y1 < y2 ? y1 : y2),
+      m_p2 (x2 > x1 ? x2 : x1, y2 > y1 ? y2 : y1)
+  {
+    //  .. nothing else ..
+  }
+
+  Box ()
+    : m_p1 (1, 1), m_p2 (-1, -1)
+  {
+    //  .. nothing else ..
+  }
+
+  inline Box &operator&= (const Box &b)
+  {
+    if (b.empty ()) {
+      *this = Box ();
+    } else if (! empty ()) {
+      Point p1 (m_p1.x () > b.m_p1.x () ? m_p1.x () : b.m_p1.x (),
+                m_p1.y () > b.m_p1.y () ? m_p1.y () : b.m_p1.y ());
+      Point p2 (m_p2.x () < b.m_p2.x () ? m_p2.x () : b.m_p2.x (),
+                m_p2.y () < b.m_p2.y () ? m_p2.y () : b.m_p2.y ());
+      m_p1 = p1;
+      m_p2 = p2;
+    }
+    return *this;
+  }
+
+  Box operator& (const Box &b) const
+  {
+    Box r (*this);
+    r &= b;
+    return r;
+  }
+
+  int width () const
+  {
+    return m_p2.x () - m_p1.x ();
+  }
+
+  int height () const
+  {
+    return m_p2.y () - m_p1.y ();
+  }
+
+  bool empty () const
+  {
+    return m_p1.x () > m_p2.x ();
+  }
+
+  std::string to_string () const
+  {
+    if (empty ()) {
+      return "()";
+    } else {
+      return "(" + m_p1.to_string () + ";" + m_p2.to_string () + ")";
+    }
+  }
+
+private:
+  Point m_p1, m_p2;
+};
+
+class Edge
+{
+public:
+  Edge ()
+    : m_p1 (0, 0), m_p2 (0, 0)
+  {
+    //  .. nothing else ..
+  }
+
+  Edge (int x1, int y1, int x2, int y2)
+    : m_p1 (x1, y1), m_p2 (x2, y2)
+  {
+    //  .. nothing else ..
+  }
+
+  Edge operator* (double s) const
+  {
+    return Edge (int (floor (m_p1.x () * s + 0.5)),
+                 int (floor (m_p1.y () * s + 0.5)),
+                 int (floor (m_p2.x () * s + 0.5)),
+                 int (floor (m_p2.y () * s + 0.5)));
+  }
+
+  int dx () const
+  {
+    return m_p2.x () - m_p1.x ();
+  }
+
+  int dy () const
+  {
+    return m_p2.y () - m_p1.y ();
+  }
+
+  std::string to_string () const
+  {
+    return "(" + m_p1.to_string () + ";" + m_p2.to_string () + ")";
+  }
+
+private:
+  Point m_p1, m_p2;
+};
+
 class BoxClassClass : public tl::VariantUserClassBase, private tl::EvalClass
 {
 public:
@@ -342,7 +466,7 @@ public:
 
 BoxClassClass BoxClassClass::instance;
 
-class BoxClass : public tl::VariantUserClassImpl<db::Box>, private tl::EvalClass
+class BoxClass : public tl::VariantUserClassImpl<Box>, private tl::EvalClass
 {
 public:
   virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const;
@@ -356,14 +480,14 @@ BoxClass BoxClass::instance;
 void BoxClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const 
 {
   if (method == "width") {
-    out = object.to_user<db::Box> ().width ();
+    out = object.to_user<Box> ().width ();
   } else if (method == "height") {
-    out = object.to_user<db::Box> ().height ();
+    out = object.to_user<Box> ().height ();
   } else if (method == "&") {
     tl_assert (args.size () == 1);
-    out = tl::Variant (new db::Box (object.to_user<db::Box> () & args[0].to_user<db::Box> ()), &BoxClass::instance, true);
+    out = tl::Variant (new Box (object.to_user<Box> () & args[0].to_user<Box> ()), &BoxClass::instance, true);
   } else if (method == "to_s") {
-    out = object.to_user<db::Box> ().to_string ();
+    out = object.to_user<Box> ().to_string ();
   } else if (method == "is_box") {
     out = true;
   } else if (method == "is_edge") {
@@ -376,7 +500,7 @@ void BoxClass::execute (const tl::ExpressionParserContext &context, tl::Variant
 void BoxClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args) const 
 {
   if (method == "new") {
-    out = tl::Variant (new db::Box (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &BoxClass::instance, true);
+    out = tl::Variant (new Box (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &BoxClass::instance, true);
   } else {
     throw tl::NoMethodError("Box", method, context);
   }
@@ -407,23 +531,23 @@ public:
 
 EdgeClassClass EdgeClassClass::instance;
 
-class EdgeClass : public tl::VariantUserClassImpl<db::Edge>,  private tl::EvalClass
+class EdgeClass : public tl::VariantUserClassImpl<Edge>,  private tl::EvalClass
 {
 public:
   virtual void execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant &object, const std::string &method, const std::vector<tl::Variant> &args) const 
   {
     if (method == "dx") {
-      out = object.to_user<db::Edge> ().dx ();
+      out = object.to_user<Edge> ().dx ();
     } else if (method == "dy") {
-      out = object.to_user<db::Edge> ().dy ();
+      out = object.to_user<Edge> ().dy ();
     } else if (method == "to_s") {
-      out = object.to_user<db::Edge> ().to_string ();
+      out = object.to_user<Edge> ().to_string ();
     } else if (method == "is_box") {
       out = false;
     } else if (method == "is_edge") {
       out = true;
     } else if (method == "*") {
-      out.set_user (new db::Edge (object.to_user<db::Edge> () * args [0].to_double ()), object.user_cls (), true);
+      out.set_user (new Edge (object.to_user<Edge> () * args [0].to_double ()), object.user_cls (), true);
     } else {
       throw tl::NoMethodError("Edge", method, context);
     }
@@ -438,22 +562,41 @@ void
 EdgeClassClass::execute (const tl::ExpressionParserContext &context, tl::Variant &out, tl::Variant & /*object*/, const std::string &method, const std::vector<tl::Variant> &args) const 
 {
   if (method == "new") {
-    out = tl::Variant (new db::Edge (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &EdgeClass::instance, true);
+    out = tl::Variant (new Edge (args[0].to_long(), args[1].to_long(), args[2].to_long(), args[3].to_long()), &EdgeClass::instance, true);
   } else {
     throw tl::NoMethodError("Edge", method, context);
   }
 }
 
+namespace tl
+{
+
+template <>
+struct type_traits <Box> : public type_traits<void>
+{
+  typedef trivial_relocate_required relocate_requirements;
+  typedef true_tag supports_to_string;
+};
+
+template <>
+struct type_traits <Edge> : public type_traits<void>
+{
+  typedef trivial_relocate_required relocate_requirements;
+  typedef true_tag supports_to_string;
+};
+
+}
+
 // basics: custom objects
 TEST(1b) 
 {
   tl::Eval e;
   tl::Variant v;
 
-  e.set_var ("XBox", tl::Variant ((db::Box *) 0, &BoxClassClass::instance, false));
-  e.set_var ("XEdge", tl::Variant ((db::Edge *) 0, &EdgeClassClass::instance, false));
-  e.set_var ("b", tl::Variant (new db::Box (0, 10, 20, 40), &BoxClass::instance, true));
-  e.set_var ("e", tl::Variant (new db::Edge (0, 10, 20, 40), &EdgeClass::instance, true));
+  e.set_var ("XBox", tl::Variant ((Box *) 0, &BoxClassClass::instance, false));
+  e.set_var ("XEdge", tl::Variant ((Edge *) 0, &EdgeClassClass::instance, false));
+  e.set_var ("b", tl::Variant (new Box (0, 10, 20, 40), &BoxClass::instance, true));
+  e.set_var ("e", tl::Variant (new Edge (0, 10, 20, 40), &EdgeClass::instance, true));
 
   v = e.parse ("b.width").execute ();
   EXPECT_EQ (v.to_string (), std::string ("20"));
@@ -1014,101 +1157,6 @@ TEST(16)
   EXPECT_EQ (v.to_string (), std::string ("true"));
 }
 
-// ref layout
-TEST(17) 
-{
-  db::Layout l;
-  l.dbu (0.05);
-  l.insert_layer (db::LayerProperties (1, 15));
-  l.insert_layer (db::LayerProperties ("name"));
-  l.add_cell ("c1");
-  l.add_cell ("c2");
-
-  tl::Eval e, ee;
-  db::LayoutContextHandler ctx (&l);
-  e.set_ctx_handler (&ctx);
-  tl::Variant v;
-
-  bool error = false;
-
-  v = e.parse ("1um").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("20"));
-  v = e.parse ("1um2").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("400"));
-  v = e.parse ("1micron").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("20"));
-  v = e.parse ("1micron2").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("400"));
-  v = e.parse ("1mic").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("20"));
-  v = e.parse ("1mic2").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("400"));
-  v = e.parse ("1m").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("20000000"));
-  v = e.parse ("1m2/1e14").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("4"));
-  v = e.parse ("1mm").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("20000"));
-  v = e.parse ("1mm2").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("400000000"));
-  v = e.parse ("50nm").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("1"));
-  v = e.parse ("<1/15>").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("0"));
-  v = e.parse ("<   name >").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("1"));
-  v = e.parse ("<'n' + 'ame'>").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("1"));
-  v = e.parse ("<<c1>>").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("0"));
-  v = e.parse ("<<  c2   >>").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("1"));
-  v = e.parse ("<<'c' + '2'>>").execute ();
-  EXPECT_EQ (v.to_string (), std::string ("1"));
-
-  error = true;
-  try {
-    v = e.parse ("60nm").execute (); // not a multiple of DBU
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-
-  error = true;
-  try {
-    v = ee.parse ("1 um").execute ();
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-
-  error = true;
-  try {
-    v = e.parse ("<1/1>").execute ();
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-
-  error = true;
-  try {
-    v = ee.parse ("<1/15>").execute ();
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-
-  error = true;
-  try {
-    v = ee.parse ("<<c1>>").execute ();
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-
-  error = true;
-  try {
-    v = e.parse ("<<c3>>").execute ();
-    error = false;
-  } catch (...) { }
-  EXPECT_EQ (error, true);
-}
-
 // polymorphic functions
 TEST(18)
 {
diff --git a/src/tl/unit_tests/tlVariant.cc b/src/tl/unit_tests/tlVariant.cc
index cdb62a453..1f9cce28c 100644
--- a/src/tl/unit_tests/tlVariant.cc
+++ b/src/tl/unit_tests/tlVariant.cc
@@ -27,10 +27,8 @@
 #include "tlObject.h"
 #include "tlTypeTraits.h"
 #include "tlUnitTest.h"
-#include "gsiDecl.h"
-#include "dbBox.h"
-#include "dbLayerProperties.h"
 #include <cstdio>
+#include <memory>
 
 struct A 
 {
@@ -793,89 +791,6 @@ TEST(2)
 }
 
 TEST(3)
-{
-  tl::Variant v;
-  v = tl::Variant::make_variant (db::Box (db::Point (0, 10), db::Point (20, 30)));
-  EXPECT_EQ (v.is_user<db::Box> (), true)
-  EXPECT_EQ (v.to_parsable_string (), "[box:(0,10;20,30)]");
-
-  std::string s = v.to_parsable_string () + "," + tl::Variant (15.0).to_parsable_string ();
-  tl::Variant vv;
-  tl::Extractor ex (s.c_str ());
-  ex.read (vv);
-  ex.test (",");
-  ex.read (v);
-  EXPECT_EQ (vv.is_user<db::Box> (), true)
-  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
-  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
-  EXPECT_EQ (std::string(v.to_string()), "15");
-}
-
-TEST(4)
-{
-  //  backward compatibility check
-  std::string s = "[box:(0,10;20,30)],##15";
-  tl::Variant vv;
-  tl::Variant v;
-  tl::Extractor ex (s.c_str ());
-  ex.read (vv);
-  ex.test (",");
-  ex.read (v);
-  EXPECT_EQ (vv.is_user<db::Box> (), true)
-  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
-  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
-  EXPECT_EQ (std::string(v.to_string()), "15");
-}
-
-TEST(5)
-{
-  //  backward compatibility check
-  std::string s = "[Box:(0,10;20,30)],##15";
-  tl::Variant vv;
-  tl::Variant v;
-  tl::Extractor ex (s.c_str ());
-  ex.read (vv);
-  ex.test (",");
-  ex.read (v);
-  EXPECT_EQ (vv.is_user<db::Box> (), true)
-  EXPECT_EQ (vv.to_parsable_string (), "[box:(0,10;20,30)]");
-  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
-  EXPECT_EQ (std::string(v.to_string()), "15");
-}
-
-TEST(6)
-{
-  //  backward compatibility check
-  std::string s = "[layer:1/0],##15";
-  tl::Variant vv;
-  tl::Variant v;
-  tl::Extractor ex (s.c_str ());
-  ex.read (vv);
-  ex.test (",");
-  ex.read (v);
-  EXPECT_EQ (vv.is_user<db::LayerProperties> (), true)
-  EXPECT_EQ (vv.to_parsable_string (), "[layer:1/0]");
-  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
-  EXPECT_EQ (std::string(v.to_string()), "15");
-}
-
-TEST(7)
-{
-  //  backward compatibility check
-  std::string s = "[LayerInfo:1/0],##15";
-  tl::Variant vv;
-  tl::Variant v;
-  tl::Extractor ex (s.c_str ());
-  ex.read (vv);
-  ex.test (",");
-  ex.read (v);
-  EXPECT_EQ (vv.is_user<db::LayerProperties> (), true)
-  EXPECT_EQ (vv.to_parsable_string (), "[layer:1/0]");
-  EXPECT_EQ ((int)v.type_code (), (int)tl::Variant::t_double);
-  EXPECT_EQ (std::string(v.to_string()), "15");
-}
-
-TEST(8)
 {
   std::string s = "'1',#1";
   tl::Variant v1;
diff --git a/src/tl/unit_tests/unit_tests.pro b/src/tl/unit_tests/unit_tests.pro
index 16cd8727a..59bcb5b09 100644
--- a/src/tl/unit_tests/unit_tests.pro
+++ b/src/tl/unit_tests/unit_tests.pro
@@ -33,12 +33,8 @@ SOURCES = \
   tlWebDAV.cc \
   tlXMLParser.cc \
 
-INCLUDEPATH += $$TL_INC $$GSI_INC
-DEPENDPATH += $$TL_INC $$GSI_INC
+INCLUDEPATH += $$TL_INC
+DEPENDPATH += $$TL_INC
 
-# because of db types support in ut:
-INCLUDEPATH += $$DB_INC
-DEPENDPATH += $$DB_INC
-
-LIBS += -L$$DESTDIR_UT -lklayout_db -lklayout_tl -lklayout_gsi
+LIBS += -L$$DESTDIR_UT -lklayout_tl