diff --git a/tests.sql b/tests.sql
index 5b38fd9..520c229 100644
--- a/tests.sql
+++ b/tests.sql
@@ -76,11 +76,23 @@ begin
   insert into wm_visuals (name, way) values('fig6-newline', st_makeline(st_endpoint(fig6b1), st_endpoint(fig6b2)));
 end $$ language plpgsql;
 
+
+drop function if exists debug_wm_get;
+create function debug_wm_get(
+  _stage text,
+  _name text,
+  OUT ways geometry[]
+) as $$
+declare
+begin
+  ways = array((select way from wm_debug where stage=_stage and name=_name));
+end $$ language plpgsql;
+
 do $$
 declare
   vbends geometry[];
 begin
-  select array((select way from wm_debug where name='fig3' and stage='bbends')) into vbends;
+  vbends = debug_wm_get('bbends', 'fig3');
   perform assert_equals(5, array_length(vbends, 1));
   perform assert_equals('LINESTRING(0 0,12 0,13 4)', st_astext(vbends[1]));
   perform assert_equals('LINESTRING(12 0,13 4,20 2,20 0)', st_astext(vbends[2]));
@@ -96,7 +108,7 @@ declare
   vbends geometry[];
   vinflections geometry[];
 begin
-  select array((select way from wm_debug where name='fig5' and stage='cinflections')) into vinflections;
+  vinflections = debug_wm_get('cinflections', 'fig5');
   perform assert_equals('LINESTRING(0 39,19 52,27 77)', st_astext(vinflections[1]));
   perform assert_equals('LINESTRING(19 52,27 77,26 104,41 115,49 115,65 103,65 75,53 45)', st_astext(vinflections[2]));
   perform assert_equals('LINESTRING(65 75,53 45,63 15,91 0)', st_astext(vinflections[3]));
@@ -116,7 +128,7 @@ declare
   vcrossings geometry[];
   mutated boolean;
 begin
-  select (self_crossing(array((select way from wm_debug where stage='cinflections' and name='fig6')))).* into vcrossings, mutated;
+  select * from self_crossing(debug_wm_get('cinflections', 'fig6')) into vcrossings, mutated;
   perform assert_equals(true, mutated);
   perform assert_equals(
     fig6,
@@ -125,7 +137,7 @@ begin
     ) from (select unnest(vcrossings) way) a)
   );
 
-  select (self_crossing(array((select way from wm_debug where stage='cinflections' and name='fig6-rev')))).* into vcrossings, mutated;
+  select * from self_crossing(debug_wm_get('cinflections', 'fig6-rev')) into vcrossings, mutated;
   perform assert_equals(true, mutated);
   perform assert_equals(
     fig6,
@@ -134,7 +146,7 @@ begin
     ) from (select unnest(vcrossings) way) a)
   );
 
-  select (self_crossing(array((select way from wm_debug where stage='cinflections' and name='fig6-combi' and gen=1)))).* into vcrossings, mutated;
+  select * from self_crossing(debug_wm_get('cinflections', 'fig6-combi')) into vcrossings, mutated;
   perform assert_equals(true, mutated);
   perform assert_equals(
     'MULTILINESTRING((84 137,91 149,114 154,120 135,125 129,141 129,147 122),(164 137,171 149,194 154,200 135,205 129,221 129,227 122))',
@@ -144,7 +156,7 @@ begin
   );
 
 
-  select (self_crossing(array((select way from wm_debug where stage='cinflections' and name='selfcrossing-1' and gen=1)))).* into vcrossings, mutated;
+  select * from self_crossing(debug_wm_get('cinflections', 'selfcrossing-1')) into vcrossings, mutated;
   perform assert_equals(true, mutated);
   perform assert_equals(
     selfcrossing1,
@@ -153,7 +165,7 @@ begin
     ) from (select unnest(vcrossings) way) a)
   );
 
-  select (self_crossing(array((select way from wm_debug where stage='cinflections' and name='selfcrossing-1-rev')))).* into vcrossings, mutated;
+  select * from self_crossing(debug_wm_get('cinflections', 'selfcrossing-1-rev')) into vcrossings, mutated;
   perform assert_equals(true, mutated);
   perform assert_equals(
     selfcrossing1,
diff --git a/wm.sql b/wm.sql
index 5e47247..e5ded07 100644
--- a/wm.sql
+++ b/wm.sql
@@ -209,6 +209,10 @@ begin
 end
 $$ language plpgsql;
 
+-- if_selfcross returns whether baseline of bendi crosses bendj.
+-- If it doesn't, returns a null geometry.
+-- Otherwise, it will return the baseline split into a few parts where it
+-- crosses bendj.
 drop function if exists if_selfcross;
 create function if_selfcross(
   bendi geometry,
@@ -217,22 +221,22 @@ create function if_selfcross(
 declare
   a geometry;
   b geometry;
-  partitions geometry;
+  multi geometry;
 begin
   a = st_pointn(bendi, 1);
   b = st_pointn(bendi, -1);
-  partitions = st_split(bendj, st_makeline(a, b));
+  multi = st_split(bendj, st_makeline(a, b));
 
-  if st_numgeometries(partitions) = 1 then
+  if st_numgeometries(multi) = 1 then
     return null;
   end if;
 
-  if st_numgeometries(partitions) = 2 and
+  if st_numgeometries(multi) = 2 and
     (st_contains(bendj, a) or st_contains(bendj, b)) then
     return null;
   end if;
 
-  return partitions;
+  return multi;
 end
 $$ language plpgsql;