Resolve issue 144

Added a test for the new mechanism
Added a gerber test file

tests/test_gerber_buffer.py

@@ -0,0 +1,44 @@
+import unittest
+import camlib
+from shapely.geometry import Polygon, LineString, Point, LinearRing
+from shapely.geometry import MultiPoint, MultiPolygon
+from shapely.geometry import box as shply_box
+from shapely.ops import cascaded_union
+import shapely.affinity as affinity
+from shapely.wkt import loads as sloads
+from shapely.wkt import dumps as sdumps
+from shapely.geometry.base import BaseGeometry
+
+class GerberBuffer(unittest.TestCase):
+    def setUp(self):
+        self.gerber1 = camlib.Gerber()
+        self.gerber1.use_buffer_for_union = True
+        self.gerber1.parse_file ("./gerber_files/STM32F4-spindle.cmp")
+        geometry1 = self.gerber1.solid_geometry
+        self.geometry1_area = self.compute_area (geometry1)
+        self.gerber2 = camlib.Gerber()
+        self.gerber2.use_buffer_for_union = False
+        self.gerber2.parse_file ("./gerber_files/STM32F4-spindle.cmp")
+        geometry2 = self.gerber2.solid_geometry
+        self.geometry2_area = self.compute_area (geometry2)
+
+
+
+    def compute_area (self, geometry):
+        area = 0
+        try:
+            for geo in geometry:
+                area += geo.area
+
+        ## Not iterable, do the actual indexing and add.
+        except TypeError:
+            area = geometry.area
+        return area
+
+
+    def test_buffer(self):
+        self.assertLessEqual (abs(self.geometry2_area - self.geometry1_area), 0.000001)
+
+
+if __name__ == '__main__':
+    unittest.main()