Added another test to drill generator and corresponding test case

src/Mod/Path/Generators/drill_generator.py

@@ -67,6 +67,9 @@ def generate(edge, dwelltime=0.0, peckdepth=0.0, repeat=1):
     ):
         raise ValueError("edge is not aligned with Z axis")
 
+    if startPoint.z < endPoint.z:
+        raise ValueError("start point is below end point")
+
     cmdParams = {}
     cmdParams["X"] = startPoint.x
     cmdParams["Y"] = startPoint.y

src/Mod/Path/PathTests/TestPathDrillGenerator.py

@@ -64,7 +64,11 @@ class TestPathDrillGenerator(PathTestUtils.PathTestBase):
         """Test edge alignment check"""
         v1 = FreeCAD.Vector(0, 10, 10)
         v2 = FreeCAD.Vector(0, 0, 0)
+        e = Part.makeLine(v1, v2)
+        self.assertRaises(ValueError, generator.generate, e)
 
+        v1 = FreeCAD.Vector(0, 0, 0)
+        v2 = FreeCAD.Vector(0, 0, 10)
         e = Part.makeLine(v1, v2)
 
         self.assertRaises(ValueError, generator.generate, e)