3 files changed, 52 insertions, 6 deletions
diff --git a/testdata/scad/features/difference-2d-tests.scad b/testdata/scad/features/difference-2d-tests.scad
new file mode 100644
index 0000000..bb798c2
--- /dev/null
+++ b/testdata/scad/features/difference-2d-tests.scad
@@ -0,0 +1,29 @@
+difference() {
+  square(10, center=true);
+  circle(r=4);
+}
+
+translate([12,0]) difference() {
+  square(10, center=true);
+  translate([2,2]) circle(r=2);
+  translate([-2,-2]) circle(r=2);
+}
+
+// Subtracting something from nothing
+translate([12,12]) difference() {
+  square([0,10], center=true);
+  # circle(r=4);
+}
+
+// Non-geometry (echo) statement as first child should be ignored
+translate([0,12]) difference() {
+  echo("difference-2d-tests");
+  square(10, center=true);
+  circle(r=4);
+}
+
+// Subtract 3D from 2D
+translate([24,0]) difference() {
+  square(10, center=true);
+  sphere(r=4);
+}
diff --git a/testdata/scad/features/difference-tests.scad b/testdata/scad/features/difference-tests.scad
index b770764..0751213 100644
--- a/testdata/scad/features/difference-tests.scad
+++ b/testdata/scad/features/difference-tests.scad
@@ -3,27 +3,26 @@ difference();
 // No children
 difference() { }
 
+// Basic
 difference() {
   cube([10,10,10], center=true);
   cylinder(r=4, h=20, center=true);
 }
 
-translate([12,0,0]) difference() {
-  cube([10,10,10], center=true);
-  cylinder(r=4, h=10.5, center=true);
-}
-
+// Two negative objects
 translate([0,12,0]) difference() {
   cube([10,10,10], center=true);
   cylinder(r=4, h=11, center=true);
   rotate([0,90,0]) cylinder(r=4, h=11, center=true);
 }
 
+// Not intersecting
 translate([12,12,0]) difference() {
   cube([10,10,10], center=true);
   translate([0,0,7.01]) cylinder(r=4, h=4, center=true);
 }
 
+// Barely intersecting
 translate([24,0,0]) difference() {
   cube([10,10,10], center=true);
   translate([0,0,6.99]) cylinder(r=4, h=4, center=true);
@@ -34,3 +33,16 @@ translate([24,12,0]) difference() {
   cube([0,10,10], center=true);
   # cylinder(r=4, h=20, center=true);
 }
+
+// Non-geometry (echo) statement as first child should be ignored
+translate([24,-12,0]) difference() {
+  echo("difference-tests");
+  cube([10,10,10], center=true);
+  cylinder(r=4, h=20, center=true);
+}
+
+// Subtracting 2D from 3D
+translate([12,0,0]) difference() {
+  cube([10,10,10], center=true);
+  circle(r=6);
+}
diff --git a/testdata/scad/features/linear_extrude-tests.scad b/testdata/scad/features/linear_extrude-tests.scad
index 680bf53..fbd1858 100644
--- a/testdata/scad/features/linear_extrude-tests.scad
+++ b/testdata/scad/features/linear_extrude-tests.scad
@@ -9,7 +9,12 @@ linear_extrude(height=10) square([10,10]);
 translate([19,5,0]) linear_extrude(height=10, center=true) difference() {circle(5); circle(3);}
 translate([31.5,2.5,0]) linear_extrude(height=10, twist=-45) polygon(points = [[-5,-2.5], [5,-2.5], [0,2.5]]);
 
-translate([0,20,0]) linear_extrude(height=20, twist=45, slices=2) square([10,10]);
+translate([0,20,0]) linear_extrude(height=20, twist=30, slices=2) {
+    difference() {
+        square([10,10]);
+        translate([1,1]) square([8,8]);
+    }
+}
 translate([19,20,0]) linear_extrude(height=20, twist=45, slices=10) square([10,10]);
 
 translate([0,-15,0]) linear_extrude(5) square([10,10]);