diff --git a/IV/Makefile b/IV/Makefile
index 9f7bae5..1209b19 100644
--- a/IV/Makefile
+++ b/IV/Makefile
@@ -1,6 +1,14 @@
 SOURCE ?= lithuania-latest.osm.pbf
 WHERE ?= name='Visinčia' OR name='Šalčia' OR name='Nemunas'
 
+.PHONY: test
+test: tests.sql .faux.db
+	./db -f tests.sql
+
+.PHONY: integration-test
+integration-test: .faux_filter_rivers
+	./db -f integration-tests.sql
+
 .faux_filter-rivers: .faux_import-osm
 	./db -v where="$(WHERE)" -f aggregate-rivers.sql
 	touch $@
diff --git a/IV/aggregate-rivers.sql b/IV/aggregate-rivers.sql
index 786c4c5..77ad483 100644
--- a/IV/aggregate-rivers.sql
+++ b/IV/aggregate-rivers.sql
@@ -6,32 +6,32 @@ declare
   cc record;
   changed boolean;
 begin
-  while (select count(1) from agg_tmp_objects) > 0 loop
-    select * from agg_tmp_objects limit 1 into c;
-    delete from agg_tmp_objects a where a.osm_id = c.osm_id;
+  while (select count(1) from aggregate_rivers_tmp) > 0 loop
+    select * from aggregate_rivers_tmp limit 1 into c;
+    delete from aggregate_rivers_tmp a where a.osm_id = c.osm_id;
     changed = true;
     while changed loop
       changed = false;
-      for cc in (select * from agg_tmp_objects a where a.name = c.name and st_dwithin(a.way, c.way, 500)) loop
+      for cc in (select * from aggregate_rivers_tmp a where a.name = c.name and st_dwithin(a.way, c.way, 500)) loop
         c.way = st_linemerge(st_union(c.way, cc.way));
-        delete from agg_tmp_objects a where a.osm_id = cc.osm_id;
+        delete from aggregate_rivers_tmp a where a.osm_id = cc.osm_id;
         changed = true;
       end loop;
     end loop; -- while changed
     return query select c.osm_id, c.name, c.way;
-  end loop; -- count(1) from agg_tmp_objects > 0
+  end loop; -- count(1) from aggregate_rivers_tmp > 0
   return;
 end
 $$ language plpgsql;
 
-create temporary table agg_tmp_objects (osm_id bigint, name text, way geometry);
-create index agg_tmp_objects_id on agg_tmp_objects(osm_id);
-create index agg_tmp_objects_gix on agg_tmp_objects using gist(way) include(name);
+create temporary table aggregate_rivers_tmp (osm_id bigint, name text, way geometry);
+create index aggregate_rivers_tmp_id on aggregate_rivers_tmp(osm_id);
+create index aggregate_rivers_tmp_gix on aggregate_rivers_tmp using gist(way) include(name);
 
-insert into agg_tmp_objects
+insert into aggregate_rivers_tmp
   select p.osm_id, p.name, p.way from planet_osm_line p
     where waterway in ('river', 'stream', 'canal') and :where;
 
 drop table if exists agg_rivers;
 create table agg_rivers as (select * from aggregate_rivers());
-drop table agg_tmp_objects;
+drop table aggregate_rivers_tmp;
diff --git a/IV/referatui.txt b/IV/referatui.txt
index e405fbf..74aa28f 100644
--- a/IV/referatui.txt
+++ b/IV/referatui.txt
@@ -35,8 +35,7 @@ analizė Lietuvos upėms.
       - grafinis palyginimas.
       - galbūt duoti kartografijos ekspertams.
 - Pritaikomumas: GDR50 ir GDR250 yra tiesiogiai pritaikomi žemėlapiams. Jei
-  algoritmas yra geresnis, žemėlapių kartografinis pagrindas gali būti
-  geresnis.
+  algoritmas yra geresnis, žemėlapių geografinis pagrindas gali būti geresnis.
 - Literatūros apžvalga (?)
 - Metodika:
   - implementacijos paaiškinimas: tai, kas neparašyta straipsnyje, bet su kuo
diff --git a/IV/wm.sql b/IV/wm.sql
index 687e0b9..0de6415 100644
--- a/IV/wm.sql
+++ b/IV/wm.sql
@@ -303,3 +303,42 @@ begin
   end if;
 end
 $$ language plpgsql;
+
+drop function if exists ST_SimplifyWM_DEBUG;
+create function ST_SimplifyWM_DEBUG(geom geometry) returns geometry as $$
+declare
+  i integer;
+  line geometry;
+  geoms geometry[];
+  bends geometry[];
+  mutated boolean;
+  l_type text;
+begin
+  l_type = st_geometrytype(geom);
+  if l_type = 'ST_LineString' then
+    geoms = array[geom];
+  elseif l_type = 'ST_MultiLineString' then
+    geoms = array((select a.geom from st_dump(geom) a order by path[1] desc));
+  else
+    raise 'Unknown geometry type %', l_type;
+  end if;
+
+  i = 1;
+  foreach line in array geoms loop
+    mutated = true;
+    while mutated loop
+      execute format('create table figures_%I (name text, i bigint, way geometry)', i);
+      execute format('insert into figures_%I select name, generate_subscripts(ways)
+      bends = detect_bends(line);
+      bends = fix_gentle_inflections(bends);
+      select * from self_crossing(bends) into bends, mutated;
+    end loop;
+  end loop;
+
+  if l_type = 'ST_LineString' then
+    return bends[1];
+  elseif l_type = 'ST_MultiLineString' then
+    return st_union(bends);
+  end if;
+end
+$$ language plpgsql;