grt/cugr: extend via_priority test to cover single-cut over default multi-cut

Signed-off-by: Eder Monteiro <emrmonteiro@precisioninno.com>

Author: eder-matheus

src/grt/test/via_priority.lef

@@ -30,9 +30,11 @@ LAYER metal2
   AREA 0.02 ;
 END metal2
 
-# Two vias for the metal1/metal2 pair, neither marked OR_DEFAULT. The larger
-# one is declared first, so a db-order pick would take it; the priority ranking
-# must instead choose VIA_SMALL (smaller enclosure).
+# Vias for the metal1/metal2 pair, none marked OR_DEFAULT. The ranking must
+# choose VIA_SMALL:
+#  - VIA_BIG is declared first, so a db-order pick would wrongly take it.
+#  - VIA_MULTI is a LEF DEFAULT via with an even smaller enclosure, so ranking
+#    the default flag before cut count would wrongly take it; single-cut must win.
 VIA VIA_BIG
   LAYER metal1 ;
     RECT -0.1 -0.15 0.1 0.15 ;
@@ -51,4 +53,14 @@ VIA VIA_SMALL
     RECT -0.075 -0.05 0.075 0.05 ;
 END VIA_SMALL
 
+VIA VIA_MULTI DEFAULT
+  LAYER metal1 ;
+    RECT -0.05 -0.05 0.05 0.05 ;
+  LAYER via12 ;
+    RECT -0.05 -0.05 -0.01 0.05 ;
+    RECT 0.01 -0.05 0.05 0.05 ;
+  LAYER metal2 ;
+    RECT -0.05 -0.05 0.05 0.05 ;
+END VIA_MULTI
+
 END LIBRARY

src/grt/test/via_priority_cugr.ok

@@ -1,4 +1,4 @@
-[INFO ODB-0227] LEF file: via_priority.lef, created 3 layers, 2 vias
+[INFO ODB-0227] LEF file: via_priority.lef, created 3 layers, 3 vias
 [INFO ODB-0128] Design: via_priority
 [INFO ODB-0130]     Created 2 pins.
 [INFO ODB-0133]     Created 1 nets and 0 connections.

src/grt/test/via_priority_cugr.tcl

@@ -1,8 +1,10 @@
-# CUGR ranks via candidates by priority (OR_DEFAULT, then LEF-default, then
-# fewest cuts, then smallest enclosure) rather than db declaration order.
-# via_priority.lef declares the larger VIA_BIG before VIA_SMALL for the
-# metal1/metal2 pair, neither marked OR_DEFAULT; the via-demand model must pick
-# VIA_SMALL. The via_geom debug line pins the chosen via and its enclosure.
+# CUGR ranks via candidates by priority (OR_DEFAULT, then fewest cuts, then
+# LEF-default, then smallest enclosure) rather than db declaration order.
+# via_priority.lef offers three metal1/metal2 vias, none OR_DEFAULT: VIA_BIG
+# (declared first, large), VIA_SMALL (single-cut, small), and VIA_MULTI (LEF
+# DEFAULT but two cuts, even smaller). The model must pick VIA_SMALL -- proving
+# db order does not win and that single-cut beats a LEF-default multi-cut via.
+# The via_geom debug line pins the chosen via and its enclosure.
 source "helpers.tcl"
 read_lef "via_priority.lef"
 read_def "via_priority.def"