Fix parenthesis bug in _isCoPlanar function (#1451)

* Add test demonstrating parenthesis bug

* Fix parenthesis bug in `_isCoPlanar` function

Author: egrim

cadquery/cq.py

@@ -570,7 +570,7 @@ def _isCoPlanar(f0, f1):
                 return False
 
             # test if p1 is on the plane of f0 (offset of planes)
-            return abs(n0.dot(p0.sub(p1)) < self.ctx.tolerance)
+            return abs(n0.dot(p0.sub(p1))) < self.ctx.tolerance
 
         def _computeXdir(normal):
             """

tests/test_cadquery.py

@@ -1613,6 +1613,10 @@ def testMultiFaceWorkplane(self):
         self.assertAlmostEqual(o.y, 0.0, 3)
         self.assertAlmostEqual(o.z, 0.5, 3)
 
+        # Test creation with non-co-planar faces fails
+        with raises(ValueError):
+            w = s.faces("+Y").workplane()
+
     def testTriangularPrism(self):
         s = Workplane("XY").lineTo(1, 0).lineTo(1, 1).close().extrude(0.2)
         self.saveModel(s)