diff --git a/test/browser/tests-browserified.js b/test/browser/tests-browserified.js
index fac186f..b3db7fd 100755
--- a/test/browser/tests-browserified.js
+++ b/test/browser/tests-browserified.js
@@ -1160,8 +1160,7 @@ module.exports = {
     [
       3, 1, 0,
       1, 1, 0,
-      1, -2, 0,
-      3, -2, 0
+      1, -2, 0
     ],
     // clockwise
     [
@@ -1174,8 +1173,10 @@ module.exports = {
     [
       -2, 3, 0,
       -2, 0, 0,
-      1, 0, 0,
-      1, -1, 0,
+      // collinear vertex
+      0, 0, 0,
+      7 / 3, 0, 0,
+      5 / 3, -1, 0,
       -3, -1, 0,
       -3, 3, 0
     ]
diff --git a/test/geometry/shared-borders.js b/test/geometry/shared-borders.js
index 1e7e80e..8009400 100644
--- a/test/geometry/shared-borders.js
+++ b/test/geometry/shared-borders.js
@@ -15,8 +15,7 @@ module.exports = {
     [
       3, 1, 0,
       1, 1, 0,
-      1, -2, 0,
-      3, -2, 0
+      1, -2, 0
     ],
     // clockwise
     [
@@ -29,8 +28,10 @@ module.exports = {
     [
       -2, 3, 0,
       -2, 0, 0,
-      1, 0, 0,
-      1, -1, 0,
+      // collinear vertex
+      0, 0, 0,
+      7 / 3, 0, 0,
+      5 / 3, -1, 0,
       -3, -1, 0,
       -3, 3, 0
     ]